Electric field-detecting optical device, tranceiver, positional information-acquiring system, and information input system

ABSTRACT

When a human hand ( 100 ) holds a transceiver ( 3   a ), the hand holds a bottom of an external wall surface and a side of the external wall surface of an insulating case ( 33 ). Therefore, a transmitting and receiving electrode ( 105 ) and an insulating film ( 107 ) cover not only the bottom of the external wall surface but also the side of the external wall surface of the insulating case ( 33 ). A first ground electrode ( 131 ), a second ground electrode ( 161 ), and a third ground electrode ( 163 ) are attached to upper portions of the internal wall surface of the insulating case ( 33 ) apart from the transmitting and receiving electrode ( 105 ). An insulating foam member ( 7   a ) is interposed between the insulating case ( 33 ) and a transceiver main body ( 30 ), and an insulating foam member ( 7   b ) is interposed between the transceiver main body ( 30 ) and a battery ( 6 ).

TECHNICAL FIELD

The present invention relates to a transceiver that is used to carry outdata communications between wearable computers, for example. Moreparticularly, the present invention relates to a transceiver that canreceive information via an electric field transmission medium byreceiving information based on an electric field induced in the electricfield transmission medium.

The present invention further relates particularly to a transceiverincluding a transceiver main body that can transmit information via anelectric field transmission medium by inducing an electric field basedon the information to be transmitted from a transmitting electrode tothe electric field transmission medium, a battery that drives thetransceiver main body, and an insulating case that incorporates thetransceiver main body.

The present invention further relates to an electric field sensor devicethat detects an electric field by modulating the optical intensity oflaser light based on an electric field to be detected, and a transceiverthat has the electric field sensor device.

The present invention further relates to positional informationobtaining system including electric field inducing means for inducing anelectric field in an electric field transmission medium corresponding toa position at which the electric field inducing means is brought intocontact with the electric field transmission medium, and a transceiverthat obtains information at the above position by receiving the electricfield induced in the electric field transmission medium and convertingthe electric field into an electric signal.

The present invention further relates to an information input systemthat obtains information based on positional information and the likefrom the positional information obtaining system.

BACKGROUND ART

In recent years, a computer with a new concept of being wearable likeclothes and able to be operated and used in this state is drawingattention. This computer is called a wearable computer, and is realizedbased on small and high-performance personal digital assistants.

Progressive researches are also conducted on a technique of carrying outdata communications between plural wearable computers via parts of ahuman body such as arms, shoulders, and bodies. This technique isalready proposed in patent literatures and the like (for example, seeJapanese Patent Application Laid-Open No. 2001-352298 (pages 4 to 5,FIGS. 1 to 5)). FIG. 1 shows an image of carrying out communicationsbetween plural wearable computers via a human body. As shown in FIG. 1,a wearable computer 1 and a transceiver 3′ that is brought into contactwith the wearable computer 1 constitute one set. A set of a wearablecomputer 1 and a transceiver 3′ can carry out data communications withother set of a wearable computer 1 and a transceiver 3′, via a humanbody. The wearable computer 1 can also carry out data communicationswith other set of a personal computer (PC) 5 which is other than thewearable computer 1 mounted on the human body and a transceiver 3′ainstalled on a wall or the like, or a set of the PC 5 and a transceiver3′b installed on a floor or the like. In this case, the PC 5 is notbrought into contact with the transceivers 3′a and 3′b unlike thewearable computer 1 and the transceiver 3′, but is connected via a cable4, to the transceivers 3′a and 3′b.

Regarding the data communications via a human body, a signal detectiontechnique according to an electro-optic method using a laser light andan electro-optic crystal is utilized. With this arrangement, an electricfield based on information (data) to be transmitted is induced in ahuman body (i.e., electric field transmission medium), and informationbased on the electric field induced in the human body is received,thereby achieving transmission and reception of the information. Thetechnique of data communications via the human body is explained indetail with reference to FIG. 2.

FIG. 2 is an overall configuration diagram of a transceiver main body30′ that is used to carry out data communications via a human body 100.As shown in FIG. 2, the transceiver main body 30′ is used in a state ofbeing in contact with the human body 100 via a transmitting andreceiving electrode 105′ and an insulating film 107′ The transceivermain body 30′ receives data supplied from the wearable computer 1 via anI/O (input/output) circuit 101, and transmits the data to a transmitter103. The transmitter 103 induces an electric field in the human body 100as an electric field transmission medium from the transmitting andreceiving electrode 105′ via the insulating film 107′. The transmitter103 transmits this electric field to other transceiver 3′ mounted onother part of the human body 100 via the human body 100.

In the transceiver main body 30′, the transmitting and receivingelectrode 105′ receives an electric field induced in the human body 100and transmitted from a separate transceiver 3′ mounted on other part ofthe human body 100 via the insulating film 107′. An electric fieldsensor unit 110′ that constitutes an electric field sensor device 115′applies the received electric field to the above electro-optic crystal,thereby generating a polarization change and an intensity change in thelaser light. A light receiving circuit 152′ that constitutes theelectric field sensor device 115′ receives the polarization-changed andintensity-changed laser light, and converts the laser light into anelectric signal, and processes this electric signal such as amplifiesthis electric signal. A signal processing circuit 116 that constitutes areceiver circuit 113 removes a frequency component other than afrequency component concerning reception information as the electricfield to be detected out of electric signals of various frequencies(i.e., extracts only the frequency component concerning the receptioninformation) with a band pass filter that constitutes the signalprocessing circuit 116, thereby removing noise from the electric signal.A waveform shaping circuit 117 that constitutes the receiver circuit 113shapes the waveform (i.e., carries out a signal processing) of theelectric signal that passes the signal processing circuit 116, andsupplies the waveform-shaped electric signal to the wearable computer 1via the input/output circuit 101.

As shown in FIG. 3, the electrode can be divided into two fortransmission and for reception, respectively. In other words, thetransmitter 103 induces an electric field in the human body 100 as anelectric field transmission medium from a transmitting electrode 105′avia an insulating film 107′a. On the other hand, a receiving electrode105′b receives an electric field induced in the human body 100 andtransmitted from a separate transceiver 3′ mounted on other part of thehuman body 100 via an insulating film 107′b. Other configurations andtheir operation are similar to those shown in FIG. 2.

For example, as shown in FIG. 1, the wearable computer 1 mounted on theright arm makes the transceiver 3′ induce an electric signal concerningtransmission data as an electric field in the human body 100 as anelectric field transmission medium, and transmit the electric field toother parts of the human body 100 as shown by a wavy line. On the otherhand, the wearable computer 1 mounted on the left arm can make thetransceiver 3′ receive the electric field transmitted from the humanbody 100, return the electric field to the electric signal, and receivereception data.

The computer such as the wearable computer 1 and a personal digitalassistant such as a portable telephone need to be compact consideringconvenience of mounting on the human body 100 and carrying as shown inFIG. 1.

However, along miniaturization of the computer and the personal digitalassistant, input of information to the computer and the personal digitalassistant become difficult.

On the other hand, the electric field sensor unit 110′ in thetransceiver main body 30′ includes ones which convert the polarizationchange of laser light into the intensity change like a polarizationmodulator, and ones which directly convert the intensity change of thelaser light like optical intensity modulators such as anelectroabsorption (EA) optical intensity modulator and a Mach-Zehnderoptical intensity modulator.

An electric field sensor unit 110′a and a light receiving circuit 152′athat use a polarization modulator 123 is explained with reference toFIG. 4 and FIG. 5, and then, an electric field sensor unit 110′b and alight receiving circuit 152′b that use an optical intensity modulator124 is explained with reference to FIG. 6 to FIG. 8.

First, as shown in FIG. 4, the electric field sensor unit 110′a usingthe polarization modulator 123 includes a current source 119, a laserdiode 121, a lens 133, the polarization modulator 123 such as anelectro-optic element (electro-optic crystal), a first and a second waveplates 135 and 137, a polarizing beam splitter 139′, and a first and asecond lenses 141a and 141 b.

The light receiving circuit 152′a includes a first photodiode 143 a, afirst load resistor 145 a, a first constant voltage source 147 a, asecond photodiode 143 b, a second load resistor 145 b, a second constantvoltage source 147 b, and a differential amplifier 112.

Of the above, the polarization modulator 123 has sensitivity in only theelectric field that is coupled in a direction perpendicular to aproceeding direction of laser light that is emitted from the laser diode121. The intensity of the electric field changes optical characteristic,that is, a birefringence index, of the polarization modulator 123. Thechange of the birefringence index of the polarization modulator 123changes the polarization of the laser light. A first electrode 125 and asecond electrode 127 are provided on both side surfaces of thepolarization modulator 123, that are opposite in a vertical direction inthe drawing. The first electrode 125 and the second electrode 127 faceeach other perpendicular to the proceeding direction of the laser lightfrom the laser diode 121 in the polarization modulator 123, and cancouple the electric field with the laser light at a right angle.

The electric field sensor unit 110′a is connected to the receivingelectrode 105′b via the first electrode 125. The second electrode 127that is opposite to the first electrode 125 is connected to a groundelectrode 131, and functions as a ground electrode to the firstelectrode 125. The receiving electrode 105′b detects an electric fieldthat is transmitted after being induced in the human body 100, transmitsthis electric field to the first electrode 125, and can couple theelectric field with the polarization modulator 123 via the firstelectrode 125.

With this arrangement, the laser light output from the laser diode 121according to the current control from the current source 119 is madeparallel light via the lens 133. The first wave plate 135 adjusts thepolarization state of the parallel laser light, and inputs the laserlight to the polarization modulator 123. The laser light that isincident to the polarization modulator 123 is propagated between thefirst and the second electrodes 125 and 127 within the polarizationmodulator 123. During the propagation of the laser light, the receivingelectrode 105′b detects the electric field that is transmitted afterbeing induced in the human body 100, and couples this electric fieldwith the polarization modulator 123 via the first electrode 125. Then,the electric field is formed from the first electrode 125 toward thesecond electrode 127 connected to the ground electrode 131. Since theelectric field is perpendicular to the proceeding direction of the laserlight that is incident from the laser diode 121 to the polarizationmodulator 123, the birefringence index as the optical characteristic ofthe polarization modulator 123 changes, and the polarization of thelaser light changes accordingly.

The second wave plate 137 adjusts the polarization state of the laserlight of which polarization is changed by the electric field from thefirst electrode 125 in the polarization modulator 123, and inputs thelaser light to the polarizing beam splitter 139′. The polarizing beamsplitter 139′ separates the laser light input from the second wave plate137, into a P wave and an S wave, and converts the laser light intooptical intensity change. The first and the second lenses 141 a and 141b condense respectively the laser light that is separated into the Pwave component and the S wave component by the polarizing beam splitter139′. The first and the second photodiodes 143 a and 143 b thatconstitute photoelectric converting means receive the laser light,convert the P wave light signal and the S wave light signal intoelectric signals respectively, and output the electric signals. Thefirst load resistor 145 a, the first constant voltage source 147 a, thesecond load resistor 145 b, and the second constant voltage source 147 bconvert the current signals output from the first and the secondphotodiodes 143 a and 143 b, into voltage signals. The differentialamplifier 112 can extract a voltage signal (intensity modulation signal)concerning reception information by differential. The extracted voltagesignal is supplied to the signal processing circuit 116 shown in FIG. 2and FIG. 3.

As shown in FIG. 5, the phase of a voltage signal Sa according to thefirst photodiode 143 a and the phase of a voltage signal Sb according tothe second photodiode 143 b are deviated by 180 degrees. Therefore, thedifferential amplifier 112 amplifies the signal component of theopposite phase, and subtracts and removes noise of the in-phase laserlight.

The signal processing circuit 116 shown in FIG. 2 and FIG. 3 removesnoise from the signal. The waveform shaping circuit 117 shapes thewaveform of the signal, and supplies the signal to the wearable computer1 via the input/output circuit 101.

The electric field sensor unit 110′b and the light receiving circuit152′b that use the optical intensity modulator 124 is explained withreference to FIG. 6 to FIG. 8. Constituent parts identical with those ofthe electric field sensor unit 110′a and the light receiving circuit152′a that use the polarization modulator 123 are assigned with the samereference numerals.

As shown in FIG. 6, the electric field sensor unit 110′b that uses theoptical intensity modulator 124 includes the current source 119, thelaser diode 121, the lens 133, the optical intensity modulator 124 suchas an electroabsorption (EA) optical intensity modulator and aMach-Zehnder optical intensity modulator, and the lens 141.

The light receiving circuit 152′b includes the photodiode 143, the loadresistor 145, the constant voltage source 147, and a (single) amplifier118.

The optical intensity modulator 124 is configured to change the opticalintensity of the light that passes due to the intensity of the coupledelectric field. The first electrode 125 and the second electrode 127 areprovided on both side surfaces of the optical intensity modulator 124,that are opposite in a vertical direction in the drawing. The firstelectrode 125 and the second electrode 127 face each other perpendicularto the proceeding direction of the laser light from the laser diode 121in the optical intensity modulator 124, and can couple the electricfield with the laser light at a right angle.

The electric field sensor unit 110′b is connected to the receivingelectrode 105′b via the first electrode 125. The second electrode 127that is opposite to the first electrode 125 is connected to the groundelectrode 131, and functions as a ground electrode to the firstelectrode 125. The receiving electrode 105′b detects an electric fieldthat is transmitted after being induced in the human body 100, transmitsthis electric field to the first electrode 125, and can couple theelectric field with the optical intensity modulator 124 via the firstelectrode 125.

An electroabsorption (EA) optical intensity modulator 124 a as oneexample of the optical intensity modulator 124 is briefly explained withreference to FIG. 7.

As shown in FIG. 7, when laser light having constant optical intensityis input, the electroabsorption optical intensity modulator 124 a variesthe optical intensity according to the detection signal concerning theelectric field with the constant optical intensity as the maximum. Inother words, the intensity of the input laser light is attenuated basedon the detection signal concerning the electric field.

A Mach-Zehnder optical intensity modulator 124 b as one example of theoptical intensity modulator 124 is briefly explained with reference toFIG. 8.

As shown in FIG. 8, the Mach-Zehnder optical intensity modulator 124 bhas two waveguides 203 a and 203 b having light refraction indexesdifferent from that of a substrate 201 formed on the substrate 201,thereby confining laser light input via a lens 205 within the waveguides203 a and 203 b and branching the laser light. The first electrode 125and the second electrode 127 apply an electric field to one of thebranched laser lights and couple the electric field with the laserlight. Thereafter, the Mach-Zehnder optical intensity modulator 124 bemits the laser light via the lens 207. When the electric field isapplied to one of the laser lights, the phase of this laser light can beslightly delayed or advanced from that of the laser light which is notapplied with the electric field.

Referring back to FIG. 6, the laser light output from the laser diode121 based on the current control by the current source 119 is madeparallel light via the lens 133. The parallel laser light is incident tothe optical intensity modulator 124. The laser light that is incident tothe optical intensity modulator 124 is propagated between the first andthe second electrodes 125 and 127 within the optical intensity modulator124. During the propagation of the laser light, the receiving electrode105′b detects the electric field that is transmitted after being inducedin the human body 100 as explained above, and couples this electricfield with the optical intensity modulator 124 via the first electrode125. Then, the electric field is formed from the first electrode 125toward the second electrode 127 connected to the ground electrode 131.Based on this coupling of the electric field, laser light of changedoptical intensity is emitted. The photodiode 143 of the light receivingcircuit 152′b receives the laser light via the lens 141. As a result,the photodiode 143 converts the laser light into a current signalaccording to the optical intensity of the laser light. The load resistor145 and the constant voltage source 147 convert the current signaloutput from the photodiode 143 into a voltage signal, and output thisvoltage signal. The output voltage signal is amplified by the amplifier118, and is supplied to the signal processing circuit 116 shown in FIG.2 and FIG. 3.

The signal processing circuit 116 shown in FIG. 2 and FIG. 3 removenoise. The waveform shaping circuit 117 shapes the waveform, andsupplies the signal to the wearable computer 1 via the input/outputcircuit 101.

However, the optical intensity modulator 124 shown in FIG. 6 cannotextract the intensity modulation signal by differential as shown in FIG.5, unlike the polarization modulator 123 shown in FIG. 4 that convertsthe polarization change of the laser light into the intensity change.Therefore, the optical intensity modulator 124 cannot carry out adifferential detection. When the photodiode 143 directly receives theoutput from the optical intensity modulator 124 without carrying out adifferential detection, noise of the laser light cannot be removed,which results in poor S/N ratio of the reception signal and degradationof communication quality.

A human hand (human body 100) may hold a set of the transceiver 3′ andthe wearable computer 1, as shown in FIG. 9. The transceiver 3′ shown inFIG. 9 has such a configuration that the transceiver main body 30′ isattached to the bottom of the internal wall surface of the insulatingcase 33 configured by an insulator, and a battery 6 that drives thetransceiver main body 30′ is attached on the upper surface of thetransceiver main body 30′. Further, the transmitting and receivingelectrode 105′ is attached to the bottom of the external wall surface ofthe insulating case 33, and this transmitting and receiving electrode105′ is covered with the insulating film 107′. Parts other than theoperation/input surface of the wearable computer 1 are covered with aninsulating case 11.

However, when the hand holds the transceiver 3′ as shown in FIG. 9, evenwhen an electric field E1 for transmission is induced in the human hand(human body 100) from the transmitting and receiving electrode 105′,electric fields E2′ and E3′ thereof return from the hand to thetransceiver 3′ via the side surface of the insulating case 33.Therefore, the transceiver 3′ does not carry out normal transmissionoperation.

DISCLOSURE OF THE INVENTION

The present invention has been achieved in the light of the abovesituation, and it is an object of the present invention to provide atechnique of normally carrying out transmission and reception operationof a transceiver even if a human body as an electric field transmissionmedium contacts a wide surface out of an external wall surface of thetransceiver, wherein the transceiver includes a transceiver main bodythat can transmit and receive information via the electric fieldtransmission medium, a battery that drives this transceiver, and aninsulating case that covers the transceiver main body.

Further, the present invention has been made in the light of the abovesituation, and has an object of suppressing degradation of communicationquality of an electric field sensor device using an optical intensitymodulator to detect an electric field and a transceiver having thiselectric field sensor device.

Further, the present invention has been made in the light of the abovesituation, and has an object of providing a technique of easilyinputting information to a computer and a personal digital assistanteach of which is used in a set with a transceiver that can transmit andreceive information via an electric field transmission medium.

In order to achieve the above objects, a first aspect of the presentinvention provides a transceiver including: a transmitting and receivingelectrode that induces an electric field in an electric fieldtransmission medium, and receives the electric field induced in saidelectric field transmission medium; a transceiver main body thatgenerates said electric field based on information to be transmitted insaid transmitting and receiving electrode, and converts said electricfield generated in said transmitting and receiving electrode intoreception information, thereby transmitting and receiving informationvia said electric field transmission medium; a first structure that isinterposed between said transmitting and receiving electrode and saidelectric field transmission medium; a second structure that isinterposed between said transceiver main body and said electric fieldtransmission medium; a battery that drives said transceiver main body;and a third structure that is interposed between said transceiver mainbody and said battery, wherein each of said first, said second, and saidthird structures is composed of at least one of metal, a semiconductor,and an insulator, and is equivalent as a parallel circuit of a resistorand a capacitor.

A second aspect of the present invention provides the transceiveraccording to the first aspect of the invention, wherein the impedance ofsaid second structure and the impedance of said third structure arelarger than the impedance of said first structure.

A third aspect of the present invention provides the transceiveraccording to the second aspect of the invention, wherein said firststructure is an insulating film that covers said transmitting andreceiving electrode against said electric field transmission medium.

A fourth aspect of the present invention provides the transceiveraccording to the second aspect of the invention, wherein said secondstructure and said third structure are insulating members.

In order to achieve the above objects, a fifth aspect of the presentinvention provides a transceiver including: a transceiver main body thatinduces an electric field based on information to be transmitted in anelectric field transmission medium from a transmitting electrode,thereby transmitting the information via said electric fieldtransmission medium; a battery that drives said transceiver main body;and an insulating case that incorporates said transceiver main body,wherein said transmitting electrode is provided on the whole surface ofa portion of an external wall surface of said insulating case, saidelectric field transmission medium closely approaching the portion, andis covered with an insulating film so as not to be in direct contactwith said electric field transmission medium.

A sixth aspect of the present invention provides the transceiveraccording to the fifth aspect of the invention, further including aninsulating member between said battery and said transceiver main body.

A seventh aspect of the present invention provides the transceiveraccording to the sixth aspect of the invention, wherein the insulatingmember is a foam member containing air.

An eighth aspect of the present invention provides the transceiveraccording to the sixth aspect of the invention, wherein said insulatingmember is a plurality of wooden pillars.

A ninth aspect of the present invention provides the transceiveraccording to the sixth aspect of the invention, wherein said insulatingmember is a cushion member having predetermined gas confined therein.

A tenth aspect of the present invention provides the transceiveraccording to the fifth aspect of the invention, further including aground electrode that defines a reference voltage which is necessary todrive said transceiver main body, and that is attached to an internalwall surface of said insulating case.

An eleventh aspect of the present invention provides the transceiveraccording to the fifth aspect of the invention, further including aground electrode that defines a reference voltage which is, necessary todrive said transceiver main body, and that is attached to an externaldevice at the outside of said insulating case.

In order to achieve the above objects, a twelfth aspect of the presentinvention provides a transceiver including: a transceiver main body thatinduces an electric field based on information to be transmitted in anelectric field transmission medium from a transmitting electrode, andreceives information based on the electric field induced in saidelectric field transmission medium with a receiving electrode, therebytransmitting and receiving the information via said electric fieldtransmission medium; a battery that drives said transceiver main body;and an insulating case that incorporates said transceiver main body,wherein said transmitting electrode is provided on the whole surface ofa portion of an external wall surface of said insulating case, saidelectric field transmission medium closely approaching the portion, andis covered with a first insulating film so as not to be in directcontact with said electric field transmission medium, and said receivingelectrode is provided on an external wall surface of said firstinsulating film, and is covered with a second insulating film so as notto be in direct contact with said electric field transmission medium.

In order to achieve the above objects, a thirteenth aspect of thepresent invention provides a transceiver including: a transceiver mainbody that induces an electric field based on information to betransmitted in an electric field transmission medium from a transmittingelectrode, and receives information based on the electric field inducedin said electric field transmission medium with a receiving electrode,thereby transmitting and receiving the information via said electricfield transmission medium; a battery that drives said transceiver mainbody; and an insulating case that incorporates said transceiver mainbody, wherein said receiving electrode is provided on the whole surfaceof a portion of an external wall surface of said insulating case, saidelectric field transmission medium closely approaching the portion, andis covered with a first insulating film so as not to be in directcontact with said electric field transmission medium, and saidtransmitting electrode is provided on an external wall surface of saidfirst insulating film, and is covered with a second insulating film soas not to be in direct contact with said electric field transmissionmedium.

In order to achieve the above objects, a fourteenth aspect of thepresent invention provides a transceiver that receives information basedon an electric field induced in an electric field transmission medium,thereby receiving information via said electric field transmissionmedium, said transceiver including: memory means for storing informationbased on two electric signals and positional information determinedaccording to the electric signal information, by relating these piecesof information to each other; electric field detecting means fordetecting an electric field transmitted after being induced in saidelectric field transmission medium, and converting a change of saidelectric field into an electric signal; a band pass filter that passesonly a signal component having a predetermined band containing said twoelectric signals out of electric signals obtained by said electric fielddetecting means; and position conversion processing means for referringto said memory means and obtaining positional information correspondingto the information based on said two electric signals that pass saidband pass filter.

A fifteenth aspect of the present invention provides the transceiveraccording to the fourteenth aspect of the invention, wherein said memorymeans stores information based on signal intensity of two electricsignals and positional information determined according to the signalintensity information, by relating these pieces of information to eachother, said band pass filter includes: a first band pass filter thatpasses only a signal component having a first band containing one ofsaid electric signals obtained by said electric field detecting means;and a second band pass filter that passes only a signal component havinga second band different from said first band containing the other ofsaid electric signals obtained by said electric field detecting means,said transceiver further comprising signal intensity measuring means formeasuring signal intensity of a signal component which passes throughsaid first band pass filter and signal intensity of a signal componentwhich passes through said second band pass filter, wherein said positionconversion processing means refers to said memory means and obtainspositional information corresponding to the information based on signalintensity of the signal component which passes through said first bandpass filter and signal intensity of the signal component which passesthrough said second band pass filter measured by said signal intensitymeasuring means.

A sixteenth aspect of the present invention provides the transceiveraccording to the fifteenth aspect of the invention, wherein said memorymeans stores information of an intensity difference between electricsignals and positional information determined according to theinformation, by relating these pieces of information to each other, andsaid position conversion processing means calculates a differencebetween intensity of the signal component which passes through saidfirst band pass filter and intensity of the signal component whichpasses through said second band pass filter measured by said signalintensity measuring means, refers to said memory means, and obtains thepositional information corresponding to the intensity difference.

A seventeenth aspect of the present invention provides the transceiveraccording to the sixteenth aspect of the invention, wherein an externaldevice can rewrite the relation between the information of the intensitydifference and the positional information stored in said memory means.

An eighteenth aspect of the present invention provides the transceiveraccording to the fifteenth aspect of the invention, wherein said memorymeans stores information of an intensity ratio between electric signalsand positional information determined according to the intensity ratioinformation, by relating these pieces of information to each other, andsaid position conversion processing means calculates a ratio ofintensity of the signal component which passes through said first bandpass filter to intensity of the signal component which passes throughsaid second band pass filter measured by said signal intensity measuringmeans, refers to said memory means, and obtains the positionalinformation corresponding to the intensity ratio.

A nineteenth aspect of the present invention provides the transceiveraccording to the eighteenth aspect of the invention, wherein an externaldevice can rewrite the relation between the information of the intensityratio and the positional information stored in said memory means.

A twentieth aspect of the present invention provides the transceiveraccording to the fourteenth aspect of the invention, wherein said memorymeans stores information based on a phase difference between twoelectric signals and positional information determined according to thephase difference information, by relating these pieces of information toeach other, said band pass filter includes: a first band pass filterthat passes only a signal component having a first band containing oneof said electric signals obtained by said electric field detectingmeans; and a second band pass filter that passes only a signal componenthaving a second band different from said first band containing the otherof said electric signals obtained by said electric field detectingmeans, the transceiver further comprising phase detecting means fordetecting a phase of the signal component which passes through saidfirst band pass filter and a phase of the signal component which passesthrough said second band pass filter, wherein said position conversionprocessing means calculates a difference between the phase of the signalcomponent which passes through said first band pass filter and the phaseof the signal component which passes through said second band passfilter detected by said phase detecting means, refers to said memorymeans, and obtains the positional information corresponding to the phasedifference.

A twenty first aspect of the present invention provides the transceiveraccording to the twentieth aspect of the invention, wherein an externaldevice can rewrite the relation between the information of the phasedifference and the positional information stored in said memory means.

In order to achieve said objects, a twenty second aspect of the presentinvention provides a positional information obtaining system including:an electric field transmission sheet that transmits an electric chargeand has any point thereon contacted by an electric field transmissionmedium; a first and a second signal generators that are disposedrespectively at different positions on said electric field transmissionsheet, and induce electric fields based on electric signals having afirst band and a second band respectively on said electric fieldtransmission sheet; and a transceiver that receives information based onan electric field induced in said electric field transmission medium,thereby receiving the information via said electric field transmissionmedium, wherein said transceiver includes: memory means for storinginformation based on two electric signals and positional informationdetermined according to the electric signal information, by relatingthese pieces of information to each other; electric field detectingmeans for detecting an electric field transmitted after being induced insaid electric field transmission medium, and converting a change of saidelectric field into an electric signal; a band pass filter that passesonly a signal component having a predetermined band containing said twoelectric signals out of electric signals obtained by said electric fielddetecting means; and position conversion processing means for referringto said memory means and obtaining the positional informationcorresponding to the information based on said two electric signals thatpass said band pass filter.

In order to achieve said objects, a twenty third aspect of the presentinvention provides an information input system including: an electricfield transmission sheet that transmits an electric charge and has anypoint thereon contacted by an electric field transmission medium; afirst and a second signal generators that are disposed respectively atdifferent positions on said electric field transmission sheet, andinduce electric fields based on electric signals having a first band anda second band respectively on said electric field transmission sheet; atransceiver that receives information based on an electric field inducedin said electric field transmission medium, thereby receiving theinformation via said electric field transmission medium, saidtransceiver including: memory means for storing information based on twoelectric signals and positional information determined according to theelectric signal information, by relating these pieces of information toeach other; electric field detecting means for detecting an electricfield transmitted after being induced in said electric fieldtransmission medium, and converting a change of said electric field intoan electric signal; a band pass filter that passes only a signalcomponent having a predetermined band containing said two electricsignals out of electric signals obtained by said electric fielddetecting means; and position conversion processing means for referringto said memory means and obtaining the positional informationcorresponding to the information based on said two electric signals thatpass said band pass filter; and a wearable computer that has computermemory means that stores positional information and input informationcorresponding to the positional information by relating these pieces ofinformation to each other, refers to said computer memory means based onthe positional information input from said transceiver, and obtains theinput information.

In order to achieve said objects, a twenty fourth aspect of the presentinvention provides an information input system including: electric fieldinducing means that is contacted or operated by an electric fieldtransmission medium, and induces an electric field in said electricfield transmission medium according to a physical quantity based on thecontact or operation; a transceiver that receives the electric fieldinduced in said electric field transmission medium, applies the electricfield to a polarization modulator or an optical intensity modulator,polarization-modulates or optical intensity-modulates laser lightaccording to the electric field, converts the polarization-modulated oroptical intensity-modulated laser light into an electric signal,extracts an electric signal having a frequency component concerning aphysical quantity based on said contact or operation from the convertedelectric signals, and outputs the electric signal concerning thephysical quantity based on said contact or operation; and informationprocessing means for inputting therein the electric signal concerningthe physical quantity based on said contact or operation from saidtransceiver, and obtains information corresponding to the physicalquantity based on said contact or operation by said electric fieldtransmission medium.

In order to achieve said objects, a twenty fifth aspect of the presentinvention provides an electric field sensor device that modulatesoptical intensity of laser light based on an electric field to bedetected, thereby detecting said electric field, said electric fieldsensor device having an electric field sensor unit and a light receivingcircuit, wherein said electric field sensor unit includes: laser lightemitting means; branching means for branching a laser light emitted fromsaid laser light emitting means into a first laser light and a secondlaser light that are different from each other; and optical intensitymodulating means with which said electric field to be detected iscoupled, that modulates the optical intensity of said first laser lightbased on said coupled electric field, and said light receiving circuitincludes: first light/voltage converting means for converting theoptical intensity of said first laser light modulated by said opticalintensity modulating means into a voltage signal; a second light/voltageconverting means for converting the optical intensity of said secondlaser light branched by said branching means into a voltage signal; anddifferential amplifying means for differentially amplifying the voltagesignal obtained by conversion by said first light/voltage convertingmeans and the voltage signal obtained by conversion by said secondlight/voltage converting means.

A twenty sixth aspect of the present invention provides the electricfield sensor device according to the twenty fifth aspect of theinvention, wherein said electric field sensor unit further includes anoptical variable attenuator that attenuates the optical intensity ofsaid second laser light obtained by branching by said branching means,and said second photoelectrical converting means inputs therein saidsecond laser light attenuated by said optical variable attenuator.

A twenty seventh aspect of the present invention provides the electricfield sensor device according to the twenty fifth aspect of theinvention, wherein said electric field sensor unit further includes afirst optical variable attenuator that attenuates the optical intensityof said first laser light obtained by branching by said branching meansat a predetermined rate, and a second optical variable attenuator thatattenuates the optical intensity of said second laser light obtained bybranching by said branching means at a rate higher than an attenuationrate of said first optical variable attenuator, said optical intensitymodulating means inputs therein said first laser light attenuated bysaid first optical variable attenuator, and said second photoelectricalconverting means inputs therein said second laser light attenuated bysaid second optical variable attenuator.

A twenty eighth aspect of the present invention provides the electricfield sensor device according to the twenty fifth aspect of theinvention, wherein said first light/voltage converting means includes:first light/current converting means for converting the opticalintensity of said first laser light modulated by said optical intensitymodulating means into a current signal; a first voltage source thatapplies an inverse bias voltage to said first light/current convertingmeans; and a first load resistor that converts said current signalobtained by conversion by said first light/current converting means intoa voltage signal, and said second light/voltage converting meansincludes: second light/current converting means for converting theintensity of said second laser light obtained by branching by saidbranching means into a current signal; a second voltage source thatapplies an inverse bias voltage to said second light/current convertingmeans; and a second load resistor that converts said current signalobtained by conversion by said second light/current converting meansinto a voltage signal.

A twenty ninth aspect of the present invention provides the electricfield sensor device according to the twenty eighth aspect of theinvention, wherein at least one of said first load resistor and saidsecond load resistor is a variable resistor.

A thirtieth aspect of the present invention provides the electric fieldsensor device according to the twenty eighth aspect of the invention,wherein at least one of said first voltage source and said secondvoltage source is a variable voltage source.

A thirty first aspect of the present invention provides the electricfield sensor device according to the twenty fifth aspect of theinvention, wherein said light receiving circuit further includesamplifying means for amplifying at least one of the voltage signalobtained by conversion by said first light/voltage converting means andthe voltage signal obtained by conversion by said second light/voltageconverting means.

In order to achieve said objects, a thirty second aspect of the presentinvention provides a transceiver that receives information based on anelectric field induced in an electric field transmission medium, therebyreceiving the information via said electric field transmission medium,said transceiver including: said electric field sensor device accordingto the twenty fifth aspect; a signal processing circuit that at leastremoves a noise from a voltage signal output from said electric fieldsensor device; noise detecting means for detecting quantity of a noisecomponent of the voltage signal output from said signal processingcircuit; and a control signal generator that generates a control signalto variably control a variable value of said electric field sensor unitor said light receiving circuit based on the detection data output fromsaid noise detecting means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an image diagram of carrying out communications between pluralwearable computers via a human body.

FIG. 2 is an overall configuration diagram of a conventional transceivermain body.

FIG. 3 is an overall configuration diagram of another conventionaltransceiver main body.

FIG. 4 is a detailed configuration diagram of an electric field sensorunit and a light receiving circuit of a conventional (polarizationmodulation type) transceiver main body.

FIG. 5 is a diagram showing a waveform of an input signal of adifferential amplifier shown in FIG. 4.

FIG. 6 is a detailed configuration diagram of an electric field sensorunit and a light receiving circuit of a conventional (optical intensitymodulation type) transceiver main body.

FIG. 7 is a principle diagram when an optical intensity modulator usedin the electric field sensor unit of the conventional (optical intensitymodulation type) transceiver main body is an electroabsorption type.

FIG. 8 is a principle diagram when the optical intensity modulator usedin the electric field sensor unit of the conventional (optical intensitymodulation type) transceiver main body is a Mach-Zehnder.

FIG. 9 is an image diagram showing a using state of a combination of atransceiver and a wearable computer that are held in a human hand.

FIG. 10 is an image diagram of a front view showing a using state of atransceiver and a wearable computer according to a first embodiment ofthe present invention.

FIG. 11 is an image diagram of a top plan view showing a using state ofthe transceiver and the wearable computer according to the firstembodiment of the present invention.

FIG. 12 is a diagram showing frequency bands for informationcommunication, a signal generator A, and a signal generator B,respectively.

FIG. 13 is an overall configuration diagram of a transceiver main bodywithin the transceiver according to the first embodiment.

FIG. 14 is an overall configuration diagram of a transceiver main bodywithin a transceiver according to a second embodiment.

FIG. 15 is a diagram showing a concrete example of an electric fieldtransmission sheet according to the first and the second embodiments.

FIG. 16 is a diagram showing a concrete example of the electric fieldtransmission sheet according to the first and the second embodiments.

FIG. 17 is a diagram showing a concrete example of the electric fieldtransmission sheet according to the first and the second embodiments.

FIG. 18 is an overall configuration diagram of a transceiver main bodyaccording to third to seventh embodiments of the present invention.

FIG. 19 is a detailed configuration diagram of an electric field sensorunit and a light receiving circuit of a transceiver main body accordingto the third embodiment.

FIG. 20 is a detailed configuration diagram of an electric field sensorunit and a light receiving circuit of a transceiver main body accordingto the fourth embodiment.

FIG. 21 is a detailed configuration diagram of an electric field sensorunit and a light receiving circuit of a transceiver main body accordingto the fifth embodiment.

FIG. 22 is a detailed configuration diagram of an electric field sensorunit and a light receiving circuit of a transceiver main body accordingto the sixth embodiment.

FIG. 23 is a detailed configuration diagram of an electric field sensorunit and a light receiving circuit of a transceiver main body accordingto the seventh embodiment.

FIG. 24 is an overall configuration diagram of a transceiver main bodyaccording to an eighth embodiment of the present invention.

FIG. 25 is a diagram showing an equivalent circuit between a human body,a transmitting and receiving electrode, and a transceiver main body.

FIG. 26 is a diagram showing an equivalent circuit between a human body,a transceiver main body, and a battery.

FIG. 27 is an overall configuration diagram of a transceiver and awearable computer according to a ninth embodiment of the presentinvention.

FIG. 28 is a functional block diagram showing mainly a function of thetransceiver main body.

FIG. 29 is a detailed configuration diagram of an electric field sensordevice.

FIG. 30 is an image diagram showing a using state of the transceiver andthe wearable computer shown in FIG. 27.

FIG. 31 is an overall configuration diagram of a transceiver and awearable computer according to a tenth embodiment of the presentinvention.

FIG. 32 is an overall configuration diagram of a transceiver and awearable computer according to an eleventh embodiment of the presentinvention.

FIG. 33 is an overall configuration diagram of a transceiver and awearable computer according to a twelfth embodiment of the presentinvention.

FIG. 34 is an overall configuration diagram of a transceiver and awearable computer according to a thirteenth embodiment of the presentinvention.

FIG. 35 is an overall configuration diagram of a transceiver and awearable computer according to a fourteenth embodiment of the presentinvention.

FIG. 36 is a diagram showing other embodiment of the present invention.

FIG. 37 is a diagram showing other embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Exemplary embodiments (hereinafter, referred to as “embodiments”)according to the present invention are explained in detail below withreference to the drawings.

A transceiver 3 according the embodiments of the present inventioninduces an electric field based on information to be transmitted in anelectric field transmission medium (such as the human body 100), andreceives information based on an electric field induced in the electricfield transmission medium, thereby transmitting and receivinginformation via the electric field transmission medium.

First, an embodiment of a transceiver that can easily input informationto a particularly miniaturized wearable computer is explained.

<First Embodiment>

A first embodiment is explained below with reference to the drawings.

FIG. 10 is an image diagram of a front view showing a using state of thetransceiver 3 and the wearable computer 1 according to the firstembodiment. FIG. 11 is an image diagram of a top plan view showing theusing state.

As shown in FIG. 10, an insulating sheet 301 is adhered to a flatsurface of a table 300, and an electric field transmission sheet 302that can transmit an electric field is adhered to a flat surface of theinsulating sheet 301. Signal generators A and B are disposed atdifferent corners on the flat surface of the electric field transmissionsheet 302. As shown in FIG. 11, when the electric field transmissionsheet 302 is rectangular, these signal generators are disposed atdifferent optional corners.

Each of the signal generators A and B has a configuration similar tothat including the transmitter 103, the transmitting electrode 105′a,and the insulating film 107′a as shown in FIG. 3, and can induce anelectric field based on an electric signal concerning transmissionfrequencies fa and fb respectively on the electric field transmissionsheet 302 as shown in FIG. 12.

FIG. 13 is an overall configuration diagram of a transceiver main body30 a within the transceiver 3 according to the present embodiment.

As shown in FIG. 13, the transceiver main body 30 a is similar to theconventional transceiver main body 30′ in that the transceiver main body30 a has the I/O (input/output) circuit 101, the transmitter 103, thetransmitting electrode 105 a, the insulating films 107 a and 107 b, thereceiving electrode 105 b, the electric field sensor device 115, thesignal processing circuit 116, and the waveform shaping circuit 117. Thetransceiver main body 30 a according to the present embodiment furtherhas band pass filters 11 a and 11 b, signal intensity measuring units 13a and 13 b, a position conversion processor 15, and a memory 17.

The I/O circuit 101 is used for the transceiver main body 30 a to inputand output information (data) to and from an external device such as thewearable computer 1. The transmitter 103 consists of a transmittercircuit that induces, based on the information (data) output from theI/O circuit 101, an electric field concerning this information in thehuman body 100. The transmitting electrode 105 a is used for thetransmitter 103 to induce an electric field in the human body 100, andis used as a transmitting antenna. The insulating film 107 a is aninsulator film disposed between the transmitting electrode 105 a and thehuman body 100, and prevents the transmitting electrode 105 a fromdirectly contacting the human body 100.

The receiving electrode 105 b is used to receive an electric fieldtransmitted after being induced in the human body 100 from the wearablecomputer 1 and the transceiver 3′ that are mounted on other part of thehuman body 100 and the PC 5 and the transceivers 3′a and 3′b, and isused as a receiving antenna. The insulating film 107 b is an insulatorfilm disposed between the receiving electrode 105 b and the human body100, like the insulating film 107 a.

The electric field sensor device 115 has a function of detecting anelectric field received by the receiving electrode 105 b, and convertingthis electric field into an electric signal as reception information.The signal processing circuit 116 consists of an amplifier 114 thatamplifies an electric signal transmitted from the electric field sensordevice 115, and a band pass filter 151. This band pass filter 151 is afilter circuit having a characteristic of limiting the band of anelectric signal output from the amplifier 114 and removes unnecessarynoise and an unnecessary signal component, thereby passing a signalcomponent of only a frequency band of a constant width (f1 to f2) forinformation communication as shown in FIG. 12 out of the electricsignals output from the amplifier 114.

The waveform shaping circuit 117 shapes the waveform (signal processing)of an electric signal transmitted from the signal processing circuit116, and supplies the processed electric signal to the wearable computer1 via the I/O circuit 101.

The band pass filter 11 a is a filter circuit having a characteristic oflimiting the band of an electric signal output from the amplifier 114and removes unnecessary noise and an unnecessary signal component,thereby passing a signal component of only a frequency band (fa) for thesignal generator A as shown in FIG. 12 out of the electric signalsoutput from the amplifier 114. The signal intensity measuring unit 13 ais a circuit that measures signal intensity of an electric signalconcerning the signal component that is passed by the band pass filter11 a.

The band pass filter 11 b is a filter circuit having a characteristic oflimiting the band of an electric signal output from the amplifier 114and removes unnecessary noise and an unnecessary signal component,thereby passing a signal component of only a frequency band (fb) for thesignal generator B as shown in FIG. 12 out of the electric signalsoutput from the amplifier 114. The signal intensity measuring unit 13 bis a circuit that measures signal intensity of an electric signalconcerning the signal component that is passed by the band pass filter11 b.

The memory 17 stores an intensity difference between two electricsignals and a specific position in a two-dimensional space by relatingthese pieces of information to each other. According to the presentembodiment, an optional position on the electric field transmissionsheet 302 shown in FIG. 10 and FIG. 11 and the intensity difference arerelated to each other in advance. An external device such as thewearable computer 1 can rewrite the relationship between the intensitydifference and the specific position stored in the memory 17, via theI/O circuit 101.

The position conversion processor 15 is a CPU (central processing unit)or the like that calculates a difference between the signal intensitymeasured by the signal intensity measuring unit 13 a and the signalintensity measured by the signal intensity measuring unit 13 b, andcollates this intensity difference with the intensity difference storedin the memory 17, thereby converting the calculated intensity differenceinto a specific position in a two-dimensional space.

A method of specifying a position using the transceiver main body 30 aand the signal generators A and B according to the present embodiment isexplained next.

As shown in FIG. 10 and FIG. 11, in the state that the signal generatorsA and B are installed on the electric field transmission sheet 302 anddriven, a person who wears the wearable computer 1 and the transceiver 3touches a specific position a on the electric field transmission sheet302. As a result, the receiving electrode 105 b receives electric fieldsfrom the signal generators A and B via the finger (human body 100) andthe insulating film 107 b. The electric field sensor device 115 couples(applies) the received electric fields to an electro-optic crystal, notshown, of the electric field sensor device 115, converts the electricfields into electric signals, and transmits the electric signals to thesignal processing circuit 116. The amplifier 114 of the signalprocessing circuit 116 amplifies the electric signals, and transmits theamplified electric signals to the band pass filter 151. However, theelectric signals concerning the electric fields from the signalgenerators A and B do not pass through the band pass filter 116.

The electric signals transmitted from the amplifier 114 are alsotransmitted to the band pass filters 11 a and 11 b.

The band pass filter 11 a passes the signal component of only the band(fa) for the signal generator A out of the electric signals concerningthe electric fields from the signal generators A and B, and transmitsthis signal component to the signal intensity measuring unit 13 a. Thesignal intensity measuring unit 13 a measures signal intensity of theelectric signal concerning the signal component that is passed by theband pass filter 11 a.

On the other hand, the band pass filter 11 b passes the signal componentof only the band (fb) for the signal generator B out of the electricsignals concerning the electric fields from the signal generators A andB, and transmits this signal component to the signal intensity measuringunit 13 b. The signal intensity measuring unit 13 b measures signalintensity of the electric signal concerning the signal component that ispassed by the band pass filter 11 b.

The position conversion processor 15 calculates an intensity differencebetween the signal intensity measured by the signal intensity measuringunit 13 a and the signal intensity measured by the signal intensitymeasuring unit 13 b, and collates this intensity difference with theintensity difference stored in the memory 17, thereby converting thecalculated intensity difference into the specific position a in thetwo-dimensional space on the electric field transmission sheet 202.

Finally, the position conversion processor 15 transmits the positioninformation (data) at the specific position a obtained by the positionconversion processor 15 to the wearable computer 1 via the I/O circuit101.

As explained above, according to the present embodiment, the intensitydifference between the signal intensity measured by the signal intensitymeasuring unit 13 a and the signal intensity measured by the signalintensity measuring unit 13 b is calculated. This intensity differenceis collated with the intensity difference stored in the memory 17,thereby converting the calculated intensity difference into the specificposition in the two-dimensional space. With this arrangement, thepositional information at the specific position a on the electric fieldtransmission sheet 302 that is touched with the finger (human body 100)can be input to the wearable computer 1 or the like. Therefore, there isan effect that information can be easily input to the wearable computer1 or the like.

In the above embodiment, the position conversion processor 15 calculatesthe intensity difference between the signal intensity measured by thesignal intensity measuring unit 13 a and the signal intensity measuredby the signal intensity measuring unit 13 b. The position conversionprocessor 15 may also calculate an intensity ratio of the signalintensity measured by the signal intensity measuring unit 13 a to thesignal intensity measured by the signal intensity measuring unit 13 b.In this case, the memory 17 needs to store the intensity ratio betweenthe two electric signals and the specific position in thetwo-dimensional space by relating these pieces of information to eachother.

<Second Embodiment>

A second embodiment is explained with reference to the drawings.

FIG. 14 is an overall configuration diagram of a transceiver main body30 b within a transceiver according to the second embodiment.Constituent parts that are identical with those according to the firstembodiment are assigned with same reference numerals, and theirexplanation is omitted.

A phase detector 23 a shown in FIG. 14 is a circuit that detects a phaseof an electric signal concerning a signal component which is passed bythe band pass filter 11 a. A phase detector 23 b is a circuit thatdetects a phase of an electric signal concerning a signal componentwhich is passed by the band pass filter 11 b.

A memory 27 stores a phase difference between two electric signals and aspecific position in a two-dimensional space by relating these pieces ofinformation to each other. According to the present embodiment, anoptional position on the electric field transmission sheet 302 shown inFIG. 10 and FIG. 11 and the phase difference are related to each otherin advance. An external device such as the wearable computer 1 canrewrite the relationship between the phase difference and the specificposition stored in the memory 27, via the I/O circuit 101.

A position conversion processor 25 is a CPU or the like that calculatesa difference between the phase measured by the phase detector 23 a andthe phase measured by the phase detector 23 b, and collates this phasedifference with the phase difference stored in the memory 27, therebyconverting the calculated phase difference into a specific position in atwo-dimensional space.

A method of specifying a position using the transceiver 30 b and thesignal generators A and B according to the present embodiment isexplained next.

As shown in FIG. 10 and FIG. 11, in the state that the signal generatorsA and B are installed on the electric field transmission sheet 302 anddriven, a person who wears the wearable computer 1 and the transceiver 3touches the specific position a on the electric field transmission sheet302. As a result, the receiving electrode 105 b receives electric fieldsfrom the signal generators A and B via the finger (human body 100) andthe insulating film 107 b. The electric field sensor device 115 couples(applies) the received electric fields to an electro-optic crystal, notshown, of the electric field sensor device 115, converts the electricfields into electric signals, and transmits the electric signals to thesignal processing circuit 116. The amplifier 114 of the signalprocessing circuit 116 amplifies the electric signals, and transmits theamplified electric signals to the band pass filter 151. However, theelectric signals concerning the electric fields from the signalgenerators A and B do not pass through the band pass filter 151.

The electric signals transmitted from the amplifier 114 are alsotransmitted to the band pass filters 11 a and 11 b.

The band pass filter 11 a passes the signal component of only the band(fa) for the signal generator A out of the electric signals concerningthe electric fields from the signal generators A and B, and transmitsthis signal component to the phase detector 23 a. The phase detector 23a detects a phase of the electric signal concerning the signal componentthat is passed by the band pass filter 11 a.

On the other hand, the band pass filter 11 b passes the signal componentof only the band (fb) for the signal generator B out of the electricsignals concerning the electric fields from the signal generators A andB, and transmits this signal component to the phase detector 23 b. Thephase detector 23 b detects a phase of the electric signal concerningthe signal component that is passed by the band pass filter 11 b.

The position conversion processor 25 calculates a phase differencebetween the phase measured by the phase detector 23 a and the phasemeasured by the phase detector 23 b, and collates this phase differencewith the phase difference stored in the memory 27, thereby convertingthe calculated phase difference into the specific position α in thetwo-dimensional space on the electric field transmission sheet 302.

Finally, the position conversion processor 25 transmits the positioninformation (data) at the specific position α obtained by the positionconversion processor 25 to the wearable computer 1 via the I/O circuit101.

As explained above, according to the present embodiment, effect similarto that according to the first embodiment is obtained.

Concrete examples according to the first and the second embodiments areexplained below with reference to FIG. 15 to FIG. 17.

FIRST EXAMPLE

FIG. 15 and FIG. 16 show an example that the above embodiments areapplied to an electric field transmission sheet 302 a and a keyboard ofa personal computer. As shown in FIG. 15, a picture of a keyboard isprinted on the electric field transmission sheet 302 a. When a persontouches a specific position α1, it is possible to specify the touchedkey based on respective distances x1 and y1 from the signal generators Aand B.

As described above, positional information, that is, the distances x1and y1 from the signal generators A and B respectively in this case, istransmitted from the transceiver 3 to the wearable computer 1. Thewearable computer 1 has a table showing a relationship between thepositional information and the input information that is the same as therelationship between the position on the electric field transmissionsheet 302 a and the print information at this position. As a result, thewearable computer 1 can understand the information that the personintends to indicate.

SECOND EXAMPLE

FIG. 17 shows an example that the above embodiments are applied to anelectric field transmission sheet 302 b such as a touch panel, a touchscreen, and a showcase. Similarly, when a person touches a specificposition α2, for example, it is possible to specify the touched positionbased on respective distances x2 and y2 from the signal generators A andB According to the above embodiments, “two signal generators” and “anelectric field transmission sheet” are used. When a person touches theelectric field transmission sheet with a hand (finger), electric signalsfrom the two signal generators are transmitted to a transceiver via thehand (human body 100). The transceiver separates the two electricsignals, and obtains information about distances from the two signalgenerators to the touched position, based on the two electric signals.The gist of the present invention is not limited to this.

For example, the present invention can be applied not only to atwo-dimensional plane surface but also to a three-dimensional space. Inother words, when “three signal generators” and a three-dimensional“electric field transmission medium” are used, the three signalgenerators can transmit signals to a finger that indicates a certainthree-dimensional point via the electric field transmission medium. Thetransceiver can separate the three signals. As a result, the transceiverobtains positional information of the point indicated by the personwithin a three-dimensional space. This information is transmitted to aninformation device such as a wearable computer. When a person indicatesa certain point within a three-dimensional space, the intendedinformation can be input to the information device.

When the transceiver has a sufficient processing speed, the transceivercan understand the information of the position of a finger asinformation about the move of the finger. In other words, for example,when the electric field transmission sheet is touched with the finger,the transceiver can understand the move of the finger in real time. Whenthis information is transmitted to an information device such as awearable computer, the move information itself or information relevantto the move information intended by a person can be input to theinformation device.

The information transmitted to the transceiver via the human body is notlimited to a signal based on which a position (speed) can be obtained.For example, when the electric field transmission sheet has a functionof detecting a pressure, the pressure signal can be also converted intoan electric field, and can be transmitted to the transceiver via afinger or the like. In this case, the transceiver can obtain theinformation of pressing force that a person intends. When thisinformation is transmitted to an information device such as a wearablecomputer, the information device can obtain information corresponding tothe pressing force.

While it is explained above that the information device such as awearable computer has information corresponding to position informationor pressure information intended by a person, the transceiver itself mayhave this information. With this arrangement, the transceiver itself canobtain information intended by a person. Alternatively, a third deviceother than the information device such as a wearable computer and thetransceiver can have this information, and the information device andthe transceiver can obtain the information from this third device.

An embodiment of a transceiver that employs an optical intensitymodulator in the electric field sensor unit is explained next.

<Third Embodiment>

An electric field sensor device 115 a, and an optical intensitymodulation transceiver (hereinafter simply referred to as a“transceiver”) 3 having the electric field sensor device 115 a accordingto a third embodiment of the present invention are explained withreference to FIG. 18 and FIG. 19.

FIG. 18 is an overall configuration diagram of a transceiver main body30 c that is used to carry out data communications via the human body100. FIG. 18 is an overall configuration diagram common to the third toseventh embodiments.

As shown in FIG. 18, the transceiver main body 30 c has the I/O(input/output) circuit 101, the transmitter 103, the transmittingelectrode 105 a, the receiving electrode 105 b, the insulating films 107a and 107 b, the electric field sensor device 115 (the electric fieldsensor unit 110, and a light receiving circuit 152), the signalprocessing circuit 116, and the waveform shaping circuit 117.

The I/O circuit 101 is used for the transceiver main body 3 c to inputand output information (data) to and from an external device such as thewearable computer 1. The transmitter 103 consists of a transmittercircuit that induces, based on the information (data) output from theI/O circuit 101, an electric field concerning this information in thehuman body 100. The transmitting electrode 105 a is used for thetransmitter 103 to induce an electric field in the human body 100, andis used as a transmitting antenna. The receiving electrode 105 b is usedto receive an electric field transmitted after being induced in thehuman body 100 from the wearable computer 1 and the transceiver 3′ thatare mounted on other part of the human body 100 and the PC 5 and thetransceivers 3′a and 3′b, and is used as a receiving antenna.

The insulating film 107 a is an insulator film disposed between thetransmitting electrode 105 a and the human body 100, and prevents thetransmitting electrode 105 a from directly contacting the human body100. The insulating film 107 b is an insulator film disposed between thereceiving electrode 105 b and the human body 100, and prevents thereceiving electrode 105 b from directly contacting the human body 100.

The electric field sensor unit 110 that constitutes the electric fieldsensor device 115 has a function of applying an electric field receivedby the receiving electrode 105 b to the laser light, thereby changingthe optical intensity of the laser light.

The light receiving circuit 152 that constitutes the electric fieldsensor device 115 has a function of receiving the laser light of whichoptical intensity is changed, converting the laser light into anelectric signal, and performing signal processing such as amplificationof this electric signal. The signal processing circuit 116 consists ofat least a band pass filter. This band pass filter removes a frequencycomponent other than a frequency component concerning receptioninformation as an electric field to be detected among electric signalshaving various frequencies (that is, takes out only the frequencycomponent concerning the reception information), thereby performingsignal processing such as removal of noise from the electric signal.

The waveform shaping circuit 117 shapes the waveform (signal processing)of an electric signal transmitted from the signal processing circuit116, and supplies the processed electric signal to the wearable computer1 via the I/O circuit 101.

The electric field sensor device 115 a according to the third embodimentas one example of the electric field sensor device 115 is explained indetail with reference to FIG. 19. The electric field sensor device 115 aaccording to the present embodiment has an electric field sensor unit110 a as one example of the electric field sensor unit 110, and a lightreceiving circuit 152 a as one example of the light receiving circuit152. The electric field sensor device 115 a is provided in thetransceiver main body 30 c as one example of the transceiver main body30.

The electric field sensor unit 110 a according to the present embodimentconsists of the current source 119, the laser diode 121, the lens 133, abeam splitter 139, the optical intensity modulator 124, and the firstand the second lenses 141 a and 141 b.

The optical intensity modulator 124 is configured to change the opticalintensity of light that passes depending on the electric field intensityto be coupled. The first electrode 125 and the second electrode 127 areprovided on both side surfaces of the optical intensity modulator 124,that are opposite in a vertical direction in the drawing. The firstelectrode 125 and the second electrode 127 sandwich from both sides theproceeding direction of the laser light from the laser diode 121 withinthe optical intensity modulator 124, and can couple the electric fieldwith the laser light at a right angle.

The electric field sensor unit 110 a is connected to the receivingelectrode 105 b via the first electrode 125. The second electrode 127that is opposite to the first electrode 125 is connected to a groundelectrode 131, and functions as a ground electrode to the firstelectrode 125. The receiving electrode 105 b detects an electric fieldthat is transmitted after being induced in the human body 100, transmitsthis electric field to the first electrode 125, and can couple theelectric field with the optical intensity modulator 124 via the firstelectrode 125.

The laser light that is output from the laser diode 121 based on thecurrent control by the current source 119 is made parallel light via thelens 133. The parallel laser light is incident to the beam splitter 139.The beam splitter 139 is an optical system that branches the incidentlaser light into two laser lights and outputs the branched lights. Afirst laser light obtained by the branching by the beam splitter 139 isincident to the first lens 141 a via the optical intensity modulator124. A second laser light obtained by the branching by the beam splitter139 is incident to the second lens 141 b not via the optical intensitymodulator 124.

The light receiving circuit 152 a has a first set including the firstphotodiode 143 a that converts the first laser light into a currentsignal according to the optical intensity of the first laser light ofwhich optical intensity is modulated by the optical intensity modulator124, the first constant voltage source 147 a that applies an inversebias voltage to the first photodiode 143 a, and the first load resistor145 a that converts the current signal obtained by conversion by thefirst photodiode 143 a into a voltage signal, and a second set includingthe second photodiode 143 b that converts the second laser light into acurrent signal according to the optical intensity of the second laserlight received via the second lens 141 b, the second constant voltagesource 147 b that applies an inverse bias voltage to the secondphotodiode 143 b, and the second load resistor 145 b that converts thecurrent signal obtained by conversion by the second photodiode 143 binto a voltage signal.

With this arrangement, the first photodiode 143 a receives the firstlaser light that passes through the optical intensity modulator 124 andthe first lens 141 a of the electric field sensor unit 110 a, and thefirst set outputs a voltage signal (including a signal component) as aresult. The second photodiode 143 b receives the second laser light thatpasses through the second lens 141 b of the electric field sensor unit110 a, and the second set outputs a voltage signal (not including asignal component) containing noise of the laser light as a result.

The light receiving circuit 152 a also has the differential amplifier112 that differentially amplifies a voltage signal obtained byconversion by the first load resistor 145 a and a voltage signalobtained by conversion by the second load resistor 145 b. Thedifferential amplifier 112 differentially amplifies the voltage signals,and supplies the output to the signal processing circuit 116 shown inFIG. 18.

As explained above, according to the present embodiment, laser light isbranched immediately before the laser light is incident to the opticalintensity modulator 124. One laser light is input to the opticalintensity modulator 124, and is used as laser light (including a signalcomponent) for detecting an electric field. The other laser light is notinput to the optical intensity modulator 124, and is used as laser light(not including a signal component) for only removing noise from thelaser light. Therefore, it is possible to remove noise from the laserlight even when the optical intensity modulator 124 is used that cannotdifferentially take out an intensity modulation signal unlike thepolarization modulator 123 that converts a polarization change of thelaser light into an intensity change.

<Fourth Embodiment>

An electric field sensor device 115 b, and the optical intensitymodulation transceiver 3 having the electric field sensor device 115 baccording to a fourth embodiment of the present invention are explainedwith reference to FIG. 20.

The electric field sensor device 115 b according to the presentembodiment has the following electric field sensor unit 110 b in placeof the electric field sensor unit 110 a of the electric field sensordevice 115 a according to the third embodiment. Constituent parts of theelectric field sensor unit 110 b that are identical with those of theelectric field sensor unit 110 a are assigned with the same referencenumerals, and their explanation is omitted. Since the light receivingcircuit 152 a according to the present embodiment has the sameconfiguration as that of the light receiving circuit 152 a according tothe first embodiment, explanation of the light receiving circuit 152 ais omitted.

As shown in FIG. 20, the electric field sensor unit 110 b according tothe present embodiment has a first optical variable attenuator 134Ainserted between the beam splitter 139 and the optical intensitymodulator 124, and has a second optical variable attenuator 134Binserted between the beam splitter 139 and the second lens 141 b. Thefirst and the second optical variable attenuators 134A and 134Battenuate the optical intensity of laser light by a predetermined rate.

However, of the two laser lights obtained by branching by the beamsplitter 139, the first laser light passes through the optical intensitymodulator 124, but the second laser light does not pass through theoptical intensity modulator 124. Since transmission efficiency of thesecond laser light is higher than that of the first laser light, bothtransmission efficiencies need to be balanced. According to the presentembodiment, attenuation of the second optical variable attenuator 134Bthrough which the second laser light passes is set larger thanattenuation of the first optical variable attenuator 134A through whichthe first laser light passes.

With this arrangement, the first optical variable attenuator 134Aattenuates the optical intensity of the first laser light obtained bybranching by the beam splitter 139, and then the first photodiode 143 aconverts the first laser light into a current signal. The second opticalvariable attenuator 134B attenuates the optical intensity of the secondlaser light obtained by branching by the beam splitter 139, and then thesecond photodiode 143 b converts the second laser light into a currentsignal. The attenuation of the laser light that passes through the firstoptical variable attenuator 134B is larger than the attenuation of thelaser light that passes through the second optical variable attenuator134A.

As explained above, according to the present embodiment, noise isremoved from the laser light, by inserting the first and the secondoptical variable attenuators 134A and 134B. Therefore, input signals tothe differential amplifier 112 can be balanced even when the laser lightis branched.

When the second optical variable attenuator 134B by itself can balanceinput signals to the differential amplifier 112, the first opticalvariable attenuator 134A can be omitted.

<Fifth Embodiment>

An electric field sensor device 115 c, and the optical intensitymodulation transceiver 3 having the electric field sensor device 115 caccording to a fifth embodiment of the present invention are explainedwith reference to FIG. 21.

The electric field sensor device 115 c according to the presentembodiment has the following light receiving circuit 152 b in place ofthe light receiving circuit 152 a of the electric field sensor device115 a according to the third embodiment. Constituent parts of the lightreceiving circuit 152 b that are identical with those of the lightreceiving circuit 152 a are assigned with the same reference numerals,and their explanation is omitted. Since the electric field sensor unit110 a according to the present embodiment has the same configuration asthat of the electric field sensor unit 110 a according to the firstembodiment, explanation of the electric field sensor unit 110 a isomitted.

As shown in FIG. 21, in place of the first and the second load resistors145 a and 145 b according to the third embodiment, the light receivingcircuit 152 b according to the present embodiment has first and secondvariable load resistors 145A and 145B respectively. The first and thesecond variable load resistors 145A and 145B have variable loadresistances, and the resistance of the second variable load resistor145B is set larger than that of the first variable load resistor 145A.

With this arrangement, voltage signals that are output from the firstphotodiode 143 a and the second photodiode 143 b can have the samesignal intensity.

As explained above, according to the present embodiment, in place of thefirst and the second load resistors 145 a and 145 b according to thefirst embodiment, the light receiving circuit 152 b has the first andthe second variable load resistors 145A and 145B respectively, therebyremoving noise from the laser light. Therefore, input signals to thedifferential amplifier 112 can be balanced even when the laser light isbranched.

When input signals to the differential amplifier 112 can be balancedusing only one of the first and the second variable load resistors 145Aand 145B, one of these variable load resistors can be omitted.

<Sixth Embodiment>

An electric field sensor device 115 d, and the optical intensitymodulation transceiver 3 having the electric field sensor device 115 daccording to a sixth embodiment of the present invention are explainedwith reference to FIG. 22.

The electric field sensor device 115 d according to the presentembodiment has the following light receiving circuit 152 c in place ofthe light receiving circuit 152 a of the electric field sensor device115 a according to the third embodiment. Constituent parts of the lightreceiving circuit 152 c that are identical with those of the lightreceiving circuit 152 a are assigned with the same reference numerals,and their explanation is omitted. Since the electric field sensor unit110 a according to the present embodiment has the same configuration asthat of the electric field sensor unit 110 a according to the firstembodiment, explanation of the electric field sensor unit 110 a isomitted.

As shown in FIG. 22, in place of the first and the second constantvoltage sources 147 a and 147 b according to the third embodiment, thelight receiving circuit 152 c according to the present embodiment hasfirst and second variable voltage sources 147A and 147B respectively.The first and the second variable voltage sources 147A and 147B havevariable voltages, and the voltage of the second variable voltage source147B is set smaller than that of the first variable voltage source 147A.

With this arrangement, voltage signals that are output from the firstphotodiode 143 a and the second photodiode 143 b can have the samesignal intensity.

As explained above, according to the present embodiment, in place of thefirst and the second constant voltage sources 147 a and 147 b accordingto the third embodiment, the light receiving circuit 152 c has the firstand second variable voltage sources 147A and 147B respectively, therebyremoving noise from the laser light. Therefore, input signals to thedifferential amplifier 112 can be balanced even when the laser light isbranched.

When input signals to the differential amplifier 112 can be balancedusing only one of the first and the second variable voltage sources 147Aand 147B, one of these variable voltage sources can be omitted.

<Seventh Embodiment>

An electric field sensor device 115 e, and the optical intensitymodulation transceiver 3 having the electric field sensor device 115 eaccording to a seventh embodiment of the present invention are explainedwith reference to FIG. 23.

The electric field sensor device 115 e according to the presentembodiment has the following light receiving circuit 152 d in place ofthe light receiving circuit 152 a of the electric field sensor device115 a according to the third embodiment. Constituent parts of the lightreceiving circuit 152 d that are identical with those of the lightreceiving circuit 152 a are assigned with the same reference numerals,and their explanation is omitted. Since the electric field sensor unit110 a according to the present embodiment has the same configuration asthat of the electric field sensor unit 110 a according to the firstembodiment, explanation of the electric field sensor unit 110 a isomitted.

As shown in FIG. 23, there are provided a first and a second variablegain amplifiers 149A and 149B that amplify voltage signals output fromthe first and the second photodiodes 143 a and 143 b respectively beforethese voltage signals are input to the differential amplifier 112. Thefirst and the second variable gain amplifiers 149A and 149B havevariable voltage gains, and the voltage gain of the second variable gainamplifier 149B is set smaller than that of the first variable gainamplifier 149A.

With this arrangement, voltage signals that are output from the firstphotodiode 143 a and the second photodiode 143 b can have the samesignal intensity.

As explained above, according to the present embodiment, there areprovided the first and the second variable gain amplifiers 149A and 149Bthat amplify voltage signals output from the first and the secondphotodiodes 143 a and 143 b respectively before these voltage signalsare input to the differential amplifier 112, thereby removing noise fromthe laser light. Therefore, input signals to the differential amplifier112 can be balanced even when the laser light is branched.

When input signals to the differential amplifier 112 can be balancedusing only one of the first and the second variable gain amplifiers 149Aand 149B, one of these variable gain amplifiers can be omitted.

For the optical intensity modulators according to the third to theseventh embodiments, an electroabsorption (EA) optical intensitymodulator, a Mach-Zehnder optical intensity modulator, and the like canbe employed as in the conventional practice.

<Eighth Embodiment>

A transceiver main body 30 d of a transceiver according to an eighthembodiment of the present invention is explained with reference to FIG.24.

The transceiver main body 30 d according to the present embodiment hasan overall configuration as shown in FIG. 24. The transceiver main body30 d excluding an electric field sensor device 215, a noise detector218, and a control signal generator 219 has the same configuration asthat of the transceiver main body 30 c according to the thirdembodiment, and therefore, identical parts are assigned with the samereference numerals and their explanation is omitted.

The transceiver main body 30 d according to the present embodiment usesany one of the electric field sensor devices 115 b to 115 e according tothe fourth to the seventh embodiments, for the electric field sensordevice 215. The transceiver main body 30 d includes the noise detector218 that detects a magnitude of noise of a voltage signal output fromthe signal processing circuit 116, and the control signal generator 219that generates a control signal to variably control variable values ofthe electric field sensor unit 110 and the light receiving circuit 152that constitute the electric field sensor device 215, based on detectiondata output from the noise detector 218. The noise detector 218 detectsa level of noise that remains in the electric signal output from thesignal processing circuit 116, that is, a level of noise that is presentin a frequency band concerning reception information as an electricfield to be detected.

The “variable value” means the following in respective embodiments.According to the fourth embodiment (FIG. 20), the variable value meansattenuation of the optical intensity of the first and the second opticalvariable attenuators 134A and 134B. According to the fifth embodiment(FIG. 21), the variable value means resistance of the first and thesecond variable load resistors 145A and 145B. According to the sixthembodiment (FIG. 22), the variable value means a voltage of the firstand the second variable voltage sources 147A and 147B. According to theseventh embodiment (FIG. 23), the variable value means a voltage gain ofthe first and the second variable gain amplifiers 113A and 113B.

As explained above, according to the present embodiment, there is aneffect that, even after the transceiver main body 30 d is manufactured,a variable value can be automatically changed and adjusted.

Next, an embodiment of a transceiver is explained, the transceiverincluding a transceiver main body that can transmit and receiveinformation via an electric field transmission medium, a battery thatdrives the transceiver main body, and an insulating case that covers thetransceiver main body, and the transceiver being of a type that a humanbody (hand) as the electric field transmission medium contacts a widesurface of an external wall surface.

The main point of the embodiment of the transceiver is explained first.Regarding the transceiver and the wearable computer shown in FIG. 9, theequivalent circuit between the human body (hand), the transmitting andreceiving electrode, the transceiver main body, and the battery isconsidered.

FIG. 25 is a diagram showing an equivalent circuit between a human body,a transmitting and receiving electrode, and a transceiver main body.

In FIG. 9, the human body 100 and the transmitting and receivingelectrode 105′ are separated by the insulating film 107′. Therefore,impedance between the human body 100 and the transmitting and receivingelectrode 105 can be expressed by the equivalent circuit as shown inFIG. 25.

In order to realize highly reliable communications via the human body100, an induced alternate current electric field (frequency f) to thehuman body 100 needs to be large. In order to increase the inducedalternate current electric field (frequency f), the impedance betweenthe human body 100 and the transmitting and receiving electrode 105needs to be small. As shown in FIG. 25, a resistance component of theimpedance between the human body 100 and the transmitting and receivingelectrode 105 is considered very large. Therefore, in order to make theimpedance small, the capacitance component needs to be set large.

In order to increase the capacitance component, it is effective to use amaterial having a large dielectric constant for the insulating film 107or decrease the thickness of the insulating film 107. It is alsoeffective to have a large area of the transmitting and receivingelectrode 105 to indirectly face the human body over a wide range.

However, when the insulating film 107 is too thin, there is a highpossibility that the human body 100 directly touches the transmittingand receiving electrode 105, and a risk that a large current flows tothe human body 100 increases. Therefore, when the area of thetransmitting and receiving electrode 105 is increased, the capacitancecan be increased while securing safety, which is preferable. When thetransmitting and receiving electrode 105 is made large, a shieldingeffect can be expected.

FIG. 26 is a diagram showing an equivalent circuit between a human body,a transceiver main body, and a battery.

In order to realize highly reliable communications via the human body100, it is necessary to avoid inducing an unnecessary alternate currentelectric field (frequency f) between the human body 100, the transceivermain body 30, and the battery 6. For this purpose, impedance betweenthese items needs to be increased, thereby decreasing mutual couplingcapacitance.

When an insulator is interposed between the items, and in order toincrease this effect, it is necessary to use an insulator having a smalldielectric constant, or decrease an area of contact between theinsulator, the human body 100, the transceiver main body 30, and thebattery 6, or increase the thickness of the insulator.

From the above viewpoint, the following embodiment is considered tocarry out secure and highly reliable communications via the human bodyin the transceiver shown in FIG. 9.

<Ninth Embodiment>

A ninth embodiment is explained below with reference to FIG. 27 to FIG.30.

FIG. 27 is an overall configuration diagram of a transceiver 3 a and thewearable computer 1 according to a ninth embodiment of the presentinvention. FIG. 28 is a functional block diagram showing mainly afunction of the transceiver main body 30. FIG. 29 is a detailedconfiguration diagram of an electric field sensor device 115′. FIG. 30is an image diagram showing a using state of the transceiver 3a and thewearable computer 1 shown in FIG. 27.

As shown in FIG. 27, the transceiver 3 a consists of the insulating case33 formed with an insulator, a device incorporated in the insulatingcase 33, and the following members attached to the outside of theinsulating case 33.

An insulating foam member 7 a that weakens electric coupling between theinsulating case 33 and the transceiver main body 30 is attached to thebottom of the internal wall surface of the insulating case 33. Thetransceiver main body 30 that carries out transmission and reception ofdata (information) to and from the wearable computer 1 is attached tothe upper surface of the insulating foam member 7 a. An insulating foammember 7 b that weakens electric coupling between the transceiver mainbody 30 and the battery 6 is attached to the upper surface of thetransceiver main body 30. The battery 6 that drives the transceiver 30is attached to the upper surface of the insulating foam member 7 b. Inother words, the insulating foam member 7 a is sandwiched (supported ina sandwiched state) between the insulating case 33 and the transceivermain body 30, and the insulating foam member 7 b is sandwiched betweenthe transceiver main body 30 and the battery 6. The insulating foammembers 7 a and 7 b are formed with numerous holes containing air.Therefore, the insulating foam member 7 a can restrict transmission ofnoise between the insulating case 33 and the transceiver main body 30.The insulating foam member 7 b can restrict transmission of noisebetween the transceiver main body 30 and the battery 6.

A first ground electrode 131 described later is extended from thetransceiver main body 30, and is attached to an upper part of theinternal wall surface of the insulating case 33 apart from thetransmitting and receiving electrode 105 in a state that the firstground electrode 131 is not in contact with other devices (such as thebattery 6, and the wearable computer 1). A second ground electrode 161and a third ground electrode 163 described later are extended from thetransceiver main body 30, and are attached to an upper part of theinternal wall surface of the insulating case 33 apart from thetransmitting and receiving electrode 105 in a state that these groundelectrodes are not in contact with other devices (such as the battery 6,and the wearable computer 1) and the first ground electrode 131.

The transmitting and receiving electrode 105 is attached to the bottomof the external wall surface and the side of the external wall surfaceof the insulating case 33, thereby covering the whole of thetransmitting and receiving electrode 105 with the insulating film 107.Parts other than the operation/input surface of the wearable computer 1are covered with the insulating case 11.

The transceiver main body 30 is similar to the conventional transceivermain body 30′ in that the transceiver main body 30 has the I/O(input/output) circuit 101, the transmitter 103, the transmitting andreceiving electrode 105, the insulating film 107, the electric fieldsensor device 115′, and the receiving circuit 113 (the signal processingcircuit 116, and the waveform shaping circuit 117). These configurationsare explained below.

The I/O circuit 101 is used for the transceiver main body 30 to inputand output information (data) to and from an external device such as thewearable computer 1. The transmitter 103 consists of a transmittercircuit that induces, based on the information (data) output from theI/O circuit 101, an electric field concerning this information in thehuman body 100. The transmitting and receiving electrode 105 is used forthe transmitter 103 to induce an electric field in the human body 100,and is used as a transmitting antenna. The transmitting and receivingelectrode 105 is also used to receive an electric field transmittedafter being induced in the human body 100, and is used as a receivingantenna. The insulating film 107 is an insulator film disposed betweenthe transmitting and receiving electrode 105 and the human body 100,thereby preventing the transmitting and receiving electrode 105 fromdirectly contacting the human body 100.

The electric field sensor device 115′ has a function of detecting anelectric field received by the transmitting and receiving electrode 105,and converting this electric field into an electric signal as receptioninformation.

The signal processing circuit 116 of the receiving circuit 113 amplifiesan electric signal transmitted from the electric field sensor unit 115′,limits the band of the electric signal, and removes unnecessary noiseand an unnecessary signal component.

The waveform shaping circuit 117 shapes the waveform (signal processing)of an electric signal transmitted from the signal processing circuit116, and supplies the processed electric signal to the wearable computer1 via the I/O circuit 101. The transmitter 103, the receiving circuit113, and the I/O circuit 101 can be driven with the battery 6.

The electric field sensor unit 115′ is explained in detail withreference to FIG. 29. This is explained again although the outline isalready explained with reference to FIG. 4.

The electric field sensor unit 115′ restores the electric field receivedby the transceiver main body 30 to the electric signal. This processingis carried out by detecting the electric field according to anelectro-optic method using laser light and an electro-optic crystal.

As shown in FIG. 29, the electric field sensor unit 115′ consists of thecurrent source 119, the laser diode 121, the electro-optic element(electro-optic crystal) 123, the first and the second wave plates 135and 137, the polarizing beam splitter 139, the plural lenses 133, 141 a,and 141 b, the photodiode 143 a and 143 b, and the first groundelectrode 131.

Of the above, the electro-optic element 123 has sensitivity in only theelectric field that is coupled in a direction perpendicular to aproceeding direction of laser light that is emitted from the laser diode121. The electro-optic element 123 changes optical characteristic, thatis, a birefringence index, according to the electric field intensity,and changes the polarization of the laser light based on the change ofthe birefringence index. The first electrode 125 and the secondelectrode 127 are provided on both side surfaces of the electro-opticelement 123, that are opposite in a vertical direction in FIG. 29. Thefirst electrode 125 and the second electrode 127 sandwich the proceedingdirection of the laser light from the laser diode 121 in theelectro-optic element 123, and can couple the electric field with thelaser light at a right angle.

The electric field sensor unit 115′ is connected to the transmitting andreceiving electrode 105 via the first electrode 125. The secondelectrode 127 that is opposite to the first electrode 125 is connectedto the first ground electrode 131, and functions as a ground electrodeto the first electrode 125. The transmitting and receiving electrode 105receives an electric field that is transmitted after being induced inthe human body 100, transmits this electric field to the first electrode125, and can couple the electric field with the electro-optic element123 via the first electrode 125.

On the other hand, the laser light output from the laser diode 121according to the current control from the current source 119 is madeparallel light via the lens 133. The first wave plate 135 adjusts thepolarization state of the parallel laser light, and inputs the laserlight to the electro-optic element 123. The laser light that is incidentto the electro-optic element 123 is propagated between the first and thesecond electrodes 125 and 127 within the electro-optic element 123.During the propagation of the laser light, the transmitting andreceiving electrode 105 receives the electric field that is transmittedafter being induced in the human body 100 as explained above, andcouples this electric field with the electro-optic element 123 via thefirst electrode 125. Then, the electric field is formed from the firstelectrode 125 toward the second electrode 127 connected to the groundelectrode 131. Since the electric field is perpendicular to theproceeding direction of the laser light that is incident from the laserdiode 121 to the electro-optic element 123, the birefringence index asthe optical characteristic of the electro-optic element 123 changes, andthe polarization of the laser light changes accordingly.

The second wave plate 137 adjusts the polarization state of the laserlight of which polarization is changed by the electric field from thefirst electrode 125 in the electro-optic element 123, and inputs thelaser light to the polarizing beam splitter 139. The polarizing beamsplitter 139 separates the laser light incident from the second waveplate 137, into a P wave and an S wave, and converts the laser lightinto optical intensity change.

The first and the second lenses 141 a and 141 b condense respectivelythe laser light that is separated into the P wave component and the Swave component by the polarizing beam splitter 139. The first and thesecond photodiodes 143 a and 143 b receive the laser light, convert theP wave light signal and the S wave light signal into respective currentsignals, and output the current signals. As described above, the currentsignals output from the first and the second photodiodes 143 a and 143 bare converted into voltage signals using resistors. Then, the signalprocessing circuit 116 shown in FIG. 28 performs signal processing ofamplification of the voltage signals and removal of noise.

According to the transceiver main body 30 of the present embodiment, thefirst ground electrode 131 that becomes a reference point of voltage forthe electric field sensor unit 115′ is extended to the outside of thetransceiver main body 30 as shown in FIG. 27. The second groundelectrode 161 that becomes a reference point of voltage for the signalprocessing circuit 116 and the third ground electrode 163 that becomes areference point of voltage for the transmitter 103 are extended incommon to the outside.

A using state of the transceiver 3 a and the wearable computer 1according to the present embodiment is explained next with reference toFIG. 30.

As shown in FIG. 30, when the human hand (human body 100) holds thetransceiver 3 a, the hand holds the bottom of the external wall surfaceand the side of the external wall surface of the insulating case 33. Inthis case, the transmitting and receiving electrode 105 and theinsulating film 107 cover not only the bottom of the external wallsurface but also the side of the external wall surface of the insulatingcase 33. Therefore, although transmission electric fields E1, E2, and E3are induced from the whole of the insulating case 33, return of a partof the electric fields from the hand to the transceiver 3 via the sidesurface of the insulating case 33 is restricted.

As explained above, according to the present embodiment, thetransmitting electrode (the transmitting and receiving electrode 105, inthis case) is attached to a wide surface, including not only the bottomsurface (bottom) but also the side surface (side) and the like, of theexternal wall surface of the insulating case 33, and is covered with theinsulating film 107. Therefore, even when the human hand holds thetransceiver 3 a, it is possible to prevent a part of the transmissionelectric fields returning from the hand back to the transceiver 3 a.

Further, because the first ground electrode 131, the second groundelectrode 161, and the third ground electrode 163 are attached to theupper parts of the internal wall surface of the insulating case 33 apartfrom the transmitting and receiving electrode 105, it is possible toprevent leakage of an unnecessary signal from the transmitting andreceiving electrode 105 to the transceiver main body 30, and the groundcan be reinforced.

Further, because the insulating foam member 7 a is sandwiched betweenthe insulating case 33 and the transceiver main body 30, and theinsulating foam member 7 b is sandwiched between the transceiver mainbody 30 and the battery 6, it is possible to restrict noise fromentering the transceiver main body 30 from the battery 6 and theinsulating case 33.

<Tenth Embodiment>

A tenth embodiment is explained below with reference to FIG. 31.

FIG. 31 is an overall configuration diagram of a transceiver 32 and thewearable computer 1 according to the tenth embodiment. Constituent partsaccording to the tenth embodiment identical with those according to theninth embodiment are assigned with the same reference numerals, andtheir explanation is omitted.

According to the present embodiment, as shown in FIG. 31, insulatingpillars 99 a and 99 b are employed in place of the insulating foammembers 7 a and 7 b according to the ninth embodiment.

According to the present embodiment, contact areas between theinsulator, the human body 100, the transceiver main body 30, and thebattery 6 are made small, respectively. Therefore, there is a furthersignificant effect that an unnecessary alternate current field is notinduced.

Wooden materials other than the foamed materials may be used for theinsulating pillars 99 a and 99 b. However, a light and stiff member likepaulownia is preferable.

While pillars are employed in the present embodiment, a block structuremay be also employed.

<Eleventh Embodiment>

An eleventh embodiment is explained below with reference to FIG. 32.

FIG. 32 is an overall configuration diagram of a transceiver 3 c and thewearable computer 1 according to the eleventh embodiment.

According to the present embodiment, as shown in FIG. 32, the second andthe third ground electrodes 161 and 163 are extended from the insulatingcase 33 of the transceiver 3 c, and are attached to the side surface(side) of the insulating case 11 of the wearable computer 1.

As explained above, according to the present embodiment, in addition tothe effect of the ninth embodiment, the second and the third groundelectrodes 161 and 163 are positioned farther from the transmitting andreceiving electrode 105 than that according to the ninth embodiment.Therefore, leakage of an unnecessary signal from the transmitting andreceiving electrode 105 to the transceiver main body 30 can be preventedmore securely, and the ground can be further reinforced.

<Twelfth Embodiment>

A twelfth embodiment is explained below with reference to FIG. 33.

FIG. 33 is an overall configuration diagram of a transceiver 3 d and thewearable computer 1 according to the twelfth embodiment. Constituentparts according to the twelfth embodiment identical with those accordingto the ninth embodiment are assigned with the same reference numerals,and their explanation is omitted.

According to the present embodiment, as shown in FIG. 33, the firstground electrode 131 is extended from the insulating case 33 of thetransceiver 3 d, and is attached to the side surface (side) of theinsulating case 11 of the wearable computer 1.

As explained above, according to the present embodiment, in addition tothe effect of the ninth embodiment, the first ground electrode 131 ispositioned farther from the transmitting and receiving electrode 105than that according to the ninth embodiment. Therefore, leakage of anunnecessary signal from the transmitting and receiving electrode 105 tothe transceiver main body 30 can be prevented more securely, and theground can be further reinforced.

<Thirteenth Embodiment>

A thirteenth embodiment is explained below with reference to FIG. 34.

FIG. 34 is an overall configuration diagram of a transceiver 3 e and thewearable computer 1 according to the thirteenth embodiment. Constituentparts according to the thirteenth embodiment identical with thoseaccording to the ninth embodiment are assigned with the same referencenumerals, and their explanation is omitted.

According to the present embodiment, as shown in FIG. 34, thetransmitting and receiving electrode 105 is divided into a transmittingelectrode 105 a exclusively used for transmission and a receivingelectrode 105 b exclusively used for reception. The transmittingelectrode 105 a is disposed at a position corresponding to thetransmitting and receiving electrode 105 shown in FIG. 31. The receivingelectrode 105 b is disposed on an external bottom surface of theinsulating film 107 a as shown in FIG. 34. The receiving electrode 105 bis also covered with the insulating film 107 b to prevent the human bodyfrom being in direct contact with the receiving electrode 105 b.According to the present embodiment, the insulating film 107 shown inFIG. 31 is expressed as the insulating film 107 a.

As explained above, according to the present embodiment, thetransmitting electrode 105 a is relatively large, and coverssubstantially the whole of the insulating case 33, and the receivingelectrode 105 b is small. Therefore, in addition to the effect of theninth embodiment, there is an effect that a rate of returning of a partof the electric fields for transmission from the hand is small.

The layout positions of the transmitting electrode 105 a and thereceiving electrode 105 b may be replaced, like a transceiver 3 f shownin FIG. 35 (a fourteenth embodiment).

<Other Embodiments>

According to the eleventh and the twelfth embodiments, one groundelectrode is attached to the side surface of the insulating case 11 ofthe wearable computer 1. However, the attaching mode is not limited tothis. The first ground electrode 131, and the second and third groundelectrodes 161 and 163 can be attached to the side surface of theinsulating case 11 of the wearable computer 1, without the first groundelectrode 131 contacted with the second and third ground electrodes 161and 163.

According to the ninth and the eleventh to the thirteenth embodiments,the insulating foam member 7 a is sandwiched between the insulating case33 and the transceiver main body 30, and the insulating foam member 7 bis sandwiched between the transceiver main body 30 and the battery 6.The layout is not limited to this. As shown in FIG. 36, an integratedinsulating foam member 8 that covers both the battery 6 and thetransceiver main body 30 without these members contacted with each othercan be used. Further, as shown in FIG. 37, a cushion insulating member 9in which gas like air is confined can be used instead of the foammember.

Industrial Applicability

As explained above, according to the present invention, there is aneffect that when an electric field transmission medium like a human bodytouches a position in a two-dimensional space, information can be easilyinput to the wearable computer 1 and the like via the electric fieldtransmission medium.

Further, according to the present invention, laser light is branched(separated) before the laser light is incident to optical intensitymodulating means. One laser light is input to the optical intensitymodulating means, and is used as laser light for detecting an electricfield. The other laser light is not input to the optical intensitymodulating means, but is used as laser light for only removing noisefrom the laser light. Therefore, there is an effect that it is possibleto remove noise from the laser light even when the optical intensitymodulating means is used that cannot differentially take out anintensity modulation signal like the modulator that converts apolarization change of the laser light into an intensity change.

Further, according to the present invention, the transmitting electrodeis attached to a wide surface, including not only the bottom surface(bottom) but also the side surface (side), of the external wall surfaceof the insulating case. Therefore, even when the human hand holds thetransceiver, it is possible to prevent a part of the transmissionelectric fields returning from the hand back to the transceiver.

1. A transceiver (3 a, 3 b, 3 c, 3 d, and 3 e) comprising: atransmitting and receiving electrode (105) that induces an electricfield in an electric field transmission medium (100), and receives theelectric field induced in said electric field transmission medium (100);a transceiver main body (30) that generates said electric field based oninformation to be transmitted in said transmitting and receivingelectrode (105), and converts said electric field generated in saidtransmitting and receiving electrode (105) into reception information,thereby transmitting and receiving information via said electric fieldtransmission medium (100); a first structure (107) that is interposedbetween said transmitting and receiving electrode (105) and saidelectric field transmission medium (100); a second structure (7 a and 99a) that is interposed between said transceiver main body (30) and saidelectric field transmission medium (100); a battery (6) that drives saidtransceiver main body (30); and a third structure (7 b and 99 b) that isinterposed between said transceiver main body (30) and said battery (6),wherein each of said first, said second, and said third structures iscomposed of at least one of metal, a semiconductor, and an insulator,and is equivalent as a parallel circuit of a resistor and a capacitor.2. The transceiver (3 a, 3 b, 3 c, 3 d, and 3 e) according to claim 1,wherein the impedance of said second structure (7 a and 99 a) and theimpedance of said third structure (7 b and 99 b) are larger than theimpedance of said first structure (107).
 3. The transceiver (3 a, 3 b, 3c, 3 d, and 3 e) according to claim 2, wherein said first structure(107) is an insulating film that covers said transmitting and receivingelectrode (105) against said electric field transmission medium (100).4. The transceiver (3 a, 3 b, 3 c, 3 d, and 3 e) according to claim 2,wherein said second structure (7 a and 99 a) and said third structure (7b and 99 b) are insulating members.
 5. A transceiver (3 a, 3 b, 3 c, 3d, and 3 e) comprising: a transceiver main body (30) that induces anelectric field based on information to be transmitted in an electricfield transmission medium (100) from a transmitting electrode (105 and105 a), thereby transmitting the information via said electric fieldtransmission medium (100); a battery (6) that drives said transceivermain body (30); and an insulating case (33) that incorporates saidtransceiver main body (30), wherein said transmitting electrode (105 and105 a) is provided on the whole surface of a portion of an external wallsurface of said insulating case (33), said electric field transmissionmedium (100) closely approaching the portion, and is covered with aninsulating film (107 and 107 a) so as not to be in direct contact withsaid electric field transmission medium (100).
 6. The transceiver (3 a,3 b, 3 c, 3 d, and 3 e) according to claim 5, further comprising aninsulating member (7 b and 99 b) between said battery (6) and saidtransceiver main body (30).
 7. The transceiver (3 a, 3 c, 3 d, and 3 e)according to claim 6, wherein said insulating member is a foam member (7b) containing air.
 8. The transceiver (3 b) according to claim 6,wherein said insulating member is a plurality of wooden pillars (99 b).9. The transceiver according to claim 6, wherein said insulating memberis a cushion member having predetermined gas confined therein.
 10. Thetransceiver (3 a, 3 b, 3 c, 3 d, and 3 e) according to claim 5, furthercomprising a ground electrode (131, 161, and 163) that defines areference voltage which is necessary to drive said transceiver main body(30), and that is attached to an internal wall surface of saidinsulating case (33).
 11. The transceiver (3 c and 3 d) according toclaim 5, further comprising a ground electrode (131, 161, and 163) thatdefines a reference voltage which is necessary to drive said transceivermain body (30), and that is attached to an external device at theoutside of said insulating case (33).
 12. A transceiver (3 e)comprising: a transceiver main body (30) that induces an electric fieldbased on information to be transmitted in an electric field transmissionmedium (100) from a transmitting electrode (105 a), and receivesinformation based on the electric field induced in said electric fieldtransmission medium (100) with a receiving electrode (105 b), therebytransmitting and receiving the information via said electric fieldtransmission medium (100); a battery (6) that drives said transceivermain body (30); and an insulating case (33) that incorporates saidtransceiver main body (30), wherein said transmitting electrode (105 a)is provided on the whole surface of a portion of an external wallsurface of said insulating case (33), said electric field transmissionmedium (100) closely approaching the portion, and is covered with afirst insulating film (107 a) so as not to be in direct contact withsaid electric field transmission medium (100), and said receivingelectrode (105 b) is provided on an external wall surface of said firstinsulating film (107 a), and is covered with a second insulating film(107 b) so as not to be in direct contact with said electric fieldtransmission medium (100).
 13. A transceiver (3 f) comprising: atransceiver main body (30) that induces an electric field based oninformation to be transmitted in an electric field transmission medium(100) from a transmitting electrode (105 a), and receives informationbased on the electric field induced in said electric field transmissionmedium (100) with a receiving electrode (105 b), thereby transmittingand receiving the information via said electric field transmissionmedium (100); a battery (6) that drives said transceiver main body (30);and an insulating case (33) that incorporates said transceiver main body(30), wherein said receiving electrode (105 b) is provided on the wholesurface of a portion of an external wall surface of said insulating case(33), said electric field transmission medium (100) closely approachingthe portion, and is covered with a first insulating film (107 a) so asnot to be in direct contact with said electric field transmission medium(100), and said transmitting electrode (105 a) is provided on anexternal wall surface of said first insulating film (107 a), and iscovered with a second insulating film (107 b) so as not to be in directcontact with said electric field transmission medium (100).
 14. Atransceiver (3) that receives information based on an electric fieldinduced in an electric field transmission medium (100), therebyreceiving the information via said electric field transmission medium(100), said transceiver (3) comprising: memory means (17) for storinginformation based on two electric signals and positional informationdetermined according to the electric signal information, by relatingthese pieces of information to each other; electric field detectingmeans (115) for detecting an electric field transmitted after beinginduced in said electric field transmission medium (100), and convertinga change of said electric field into an electric signal; a band passfilter (11 a and 11 b) that passes only a signal component having apredetermined band containing said two electric signals out of electricsignals obtained by said electric field detecting means (115); andposition conversion processing means (15) for referring to said memorymeans (17) and obtaining positional information corresponding to theinformation based on said two electric signals that pass said band passfilter.
 15. The transceiver (3) according to claim 14, wherein saidmemory means (17) stores information based on signal intensity of twoelectric signals and positional information determined according to thesignal intensity information, by relating these pieces of information toeach other, said band pass filter (11 a and 11 b) includes: a first bandpass filter (11 a) that passes only a signal component having a firstband containing one of said electric signals obtained by said electricfield detecting means (115); and a second band pass filter (11 b) thatpasses only a signal component having a second band different from saidfirst band containing the other of said electric signals obtained bysaid electric field detecting means (115), said transceiver (3) furthercomprising signal intensity measuring means (13 a and 13 b) formeasuring signal intensity of a signal component which passes throughsaid first band pass filter (11 a) and signal intensity of a signalcomponent which passes through said second band pass filter (11 b),wherein said position conversion processing means (15) refers to saidmemory means (17) and obtains positional information corresponding tothe information based on signal intensity of a signal component whichpasses through said first band pass filter and signal intensity of asignal component which passes through said second band pass filtermeasured by said signal intensity measuring means (13 a and 13 b). 16.The transceiver (3) according to claim 15, wherein said memory means(17) stores information of an intensity difference between electricsignals and positional information determined according to the intensitydifference information, by relating these pieces of information to eachother, and said position conversion processing means (15) calculates adifference between intensity of the signal component which passesthrough said first band pass filter and intensity of the signalcomponent which passes through said second band pass filter measured bysaid signal intensity measuring means (13 a and 13 b), refers to saidmemory means (17), and obtains the positional information correspondingto the intensity difference.
 17. The transceiver (3) according to claim16, wherein an external device can rewrite the relation between theinformation of the intensity difference and the positional informationstored in said memory means (17).
 18. The transceiver (3) according toclaim 15, wherein said memory means (17) stores information of anintensity ratio between electric signals and positional informationdetermined according to the intensity ratio information, by relatingthese pieces of information to each other, and said position conversionprocessing means (15) calculates a ratio of intensity of the signalcomponent which passes through said first band pass filter to intensityof the signal component which passes through said second band passfilter measured by said signal intensity measuring means (13 a and 13b), refers to said memory means (17), and obtains the positionalinformation corresponding to the intensity ratio.
 19. The transceiver(3) according to claim 18, wherein an external device can rewrite therelation between the information of the intensity ratio and thepositional information stored in said memory means (17).
 20. Thetransceiver (3) according to claim 14, wherein said memory means (17)stores information based on a phase difference between two electricsignals and positional information determined according to the phasedifference information, by relating these pieces of information to eachother, said band pass filter (11 a and 11 b) includes: a first band passfilter (11 a) that passes only a signal component having a first bandcontaining one of said electric signals obtained by said electric fielddetecting means (115); and a second band pass filter (11 b) that passesonly a signal component having a second band different from said firstband containing the other of said electric signals obtained by saidelectric field detecting means (115), the transceiver (3) furthercomprising phase detecting means (23 a and 23 b) for detecting a phaseof the signal component which passes through said first band pass filter(11 a) and a phase of the signal component which passes through saidsecond band pass filter (11 b), wherein said position conversionprocessing means (25) calculates a difference between the phase of thesignal component which passes through said first band pass filter andthe phase of the signal component which passes through said second bandpass filter detected by said phase detecting means (23 a and 23 b),refers to said memory means (17), and obtains the positional informationcorresponding to the phase difference.
 21. The transceiver (3) accordingto claim 20, wherein an external device can rewrite the relation betweenthe information of the phase difference and the positional informationstored in said memory means (17).
 22. A positional information obtainingsystem comprising: an electric field transmission sheet (302 a) thattransmits an electric charge and has any point thereon contacted by anelectric field transmission medium (100); a first and a second signalgenerators (A and B) is that are disposed respectively at differentpositions on said electric field transmission sheet (302 a), and induceelectric fields based on electric signals having a first band and asecond band respectively on said electric field transmission sheet (302a); and a transceiver (3) that receives information based on an electricfield induced in said electric field transmission medium (100), therebyreceiving the information via said electric field transmission medium(100), wherein said transceiver (3) includes: memory means (17) forstoring information based on two electric signals and positionalinformation determined according to the electric signal information, byrelating these pieces of information to each other; electric fielddetecting means (115) for detecting an electric field transmitted afterbeing induced in said electric field transmission medium (100), andconverting a change of said electric field into an electric signal; aband pass filter (11 a and 11 b) that passes only a signal componenthaving a predetermined band containing said two electric signals out ofelectric signals obtained by said electric field detecting means (115);and position conversion processing means (15) for referring to saidmemory means (17) and obtaining the positional information correspondingto the information based on said two electric signals that pass saidband pass filter.
 23. An information input system comprising: anelectric field transmission sheet (302 a) that transmits an electriccharge and has any point thereon contacted by an electric fieldtransmission medium (100); a first and a second signal generators (A andB) that are disposed respectively at different positions on saidelectric field transmission sheet (302 a), and induce electric fieldsbased on electric signals having a first band and a second bandrespectively on said electric field transmission sheet (302 a); atransceiver (3) that receives information based on an electric fieldinduced in said electric field transmission medium (100), therebyreceiving the information via said electric field transmission medium(100), said transceiver (3) including: memory means (17) for storinginformation based on two electric signals and positional informationdetermined according to the electric signal information, by relatingthese pieces of information to each other; electric field detectingmeans (115) for detecting an electric field transmitted after beinginduced in said electric field transmission medium (100), and convertinga change of said electric field into an electric signal; a band passfilter (11 a and 11 b) that passes only a signal component having apredetermined band containing said two electric signals out of electricsignals obtained by said electric field detecting means (115); andposition conversion processing means (15) for referring to said memorymeans (17) and obtaining the positional information corresponding to theinformation based on said two electric signals that pass said band passfilter; and a wearable computer (1) that has computer memory means forstoring positional information and input information corresponding tothe positional information by relating these pieces of information toeach other, refers to said computer memory means based on the positionalinformation input from said transceiver (3), and obtains the inputinformation.
 24. An information input system comprising: electric fieldinducing means that is contacted or operated by an electric fieldtransmission medium (100), and induces an electric field in saidelectric field transmission medium (100) according to a physicalquantity based on the contact or operation; a transceiver that receivesthe electric field induced in said electric field transmission medium(100), applies the electric field to a polarization modulator or anoptical intensity modulator, polarization-modulates or opticalintensity-modulates laser light according to the electric field,converts the polarization-modulated or optical intensity-modulated laserlight into an electric signal, extracts an electric signal having afrequency component concerning a physical quantity based on said contactor operation from the converted electric signals, and outputs theelectric signal concerning the physical quantity based on said contactor operation; and information processing means for inputting therein theelectric signal concerning the physical quantity based on said contactor operation from said transceiver, and obtaining informationcorresponding to the physical quantity based on said contact oroperation by said electric field transmission medium (100).
 25. Anelectric field sensor device (115 a, 115 b, 115 c, 115 d, and 115 e)that modulates optical intensity of laser light based on an electricfield to be detected, thereby detecting said electric field, saidelectric field sensor device having an electric field sensor unit (110 aand 110 b) and a light receiving circuit (152 a, 152 b, 152 c, and 152d), wherein said electric field sensor unit (115 a, 115 b, 115 c, 115 d,and 115 e) includes: laser light emitting means (121); branching means(139) for branching a laser light emitted from said laser light emittingmeans (121) into a first laser light and a second laser light that aredifferent from each other; and optical intensity modulating means (124)with which said electric field to be detected is coupled, that modulatesthe optical intensity of said first laser light based on said coupledelectric field, and said light receiving circuit (152 a, 152 b, 152 c,and 152 d) includes: first light/voltage converting means (143 a, 147 a,147A, 145 a, and 145A) for converting the optical intensity of saidfirst laser light modulated by said optical intensity modulating means(124) into a voltage signal; second light/voltage converting means (143b, 147 b, 147B, 145 b, and 145B) for converting the optical intensity ofsaid second laser light branched by said branching means (139) into avoltage signal; and differential amplifying means (112) fordifferentially amplifying the voltage signal obtained by conversion bysaid first light/voltage converting means (143 a, 147 a, 147A, 145 a,and 145A) and the voltage signal obtained by conversion by said secondlight/voltage converting means (143 b, 147 b, 147B, 145 b, and 145B).26. The electric field sensor device (115 b) according to claim 25,wherein said electric field sensor unit (110 b) further includes anoptical variable attenuator (134B) that attenuates the optical intensityof said second laser light obtained by branching by said branching means(139), and said second photoelectrical converting means (143 b) inputssaid second laser light attenuated by said optical variable attenuator(134B).
 27. The electric field sensor device (115 b) according to claim25, wherein said electric field sensor unit (110 b) further includes afirst optical variable attenuator (134A) that attenuates the opticalintensity of said first laser light obtained by branching by saidbranching means (139) at a predetermined rate, and a second opticalvariable attenuator (134B) that attenuates the optical intensity of saidsecond laser light obtained by branching by said branching means (139)at a rate higher than an attenuation rate of said first optical variableattenuator, said optical intensity modulating means (124) inputs thereinsaid first laser light attenuated by said first optical variableattenuator (134A), and said second photoelectrical converting means (143b) inputs therein said second laser light attenuated by said secondoptical variable attenuator (134B).
 28. The electric field sensor device(115 a, 115 b, 115 c, 115 d, and 115 e) according to claim 25, whereinsaid first light/voltage converting means (143 a, 147 a, 147A, 145 a,and 145A) includes: first light/current converting means (143 a) forconverting the optical intensity of said first laser light modulated bysaid optical intensity modulating means (124) into a current signal; afirst voltage source (147 a and 147A) that applies an inverse biasvoltage to said first light/current converting means (143 a); and afirst load resistor (145 a and 145A) that converts said current signalobtained by conversion by said first light/current converting means (143a) into a voltage signal, and said second light/voltage converting means(143 b, 147 b, 147B, 145 b, and 145B) includes: second light/currentconverting means (143 b) for converting the intensity of said secondlaser light obtained by branching by said branching means (139) into acurrent signal; a second voltage source (147 b and 147B) that applies aninverse bias voltage to said second light/current converting means (143b); and a second load resistor (145 b and 145B) that converts saidcurrent signal obtained by conversion by said second light/currentconverting means (143 b) into a voltage signal.
 29. The electric fieldsensor device (115 c) according to claim 28, wherein at least one ofsaid first load resistor and said second load resistor is a variableresistor (145A and 145B).
 30. The electric field sensor device (115 d)according to claim 28, wherein at least one of said first voltage sourceand said second voltage source is a variable voltage source (147A and147B).
 31. The electric field sensor device (115 e) according to claim25, wherein said light receiving circuit (152 d) further includesamplifying means (149A and 149B) for amplifying at least one of thevoltage signal obtained by conversion by said first light/voltageconverting means (143 a, 147 a, 147A, 145 a, and 145A) and the voltagesignal obtained by conversion by said second light/voltage convertingmeans (143 b, 147 b, 147B, 145 b, and 145B).
 32. A transceiver thatreceives information based on an electric field induced in an electricfield transmission medium (100), thereby receiving the information viasaid electric field transmission medium (100), said transceivercomprising: said electric field sensor device (115 and 215) according toclaim 25; a signal processing circuit (116) that at least removes anoise from a voltage signal output from said electric field sensordevice (115 and 215); noise detecting means (218) for detecting quantityof a noise component of the voltage signal output from said signalprocessing circuit (116); and a control signal generator (219) thatgenerates a control signal to variably control a variable value of saidelectric field sensor unit (110) or said light receiving circuit (152)based on the detection data output from said noise detecting means(218).